Synthesis and Applications of IIIâV Nanowires | Chemical Reviews

Review pubs.acs.org/CR

Cite This: Chem. Rev. XXXX, XXX, XXX−XXX

Synthesis and Applications of III−V Nanowires Enrique Barrigón,*,† Magnus Heurlin,†,‡ Zhaoxia Bi,† Bo Monemar,† and Lars Samuelson*,† †

Division of Solid State Physics and NanoLund, Lund University, Box 118, 22100 Lund, Sweden Sol Voltaics AB, Scheelevägen 63, 223 63 Lund, Sweden

Downloaded via UNIV AUTONOMA DE COAHUILA on August 6, 2019 at 15:11:06 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

ABSTRACT: Low-dimensional semiconductor materials structures, where nanowires are needle-like one-dimensional examples, have developed into one of the most intensely studied fields of science and technology. The subarea described in this review is compound semiconductor nanowires, with the materials covered limited to III−V materials (like GaAs, InAs, GaP, InP,...) and III-nitride materials (GaN, InGaN, AlGaN,...). We review the way in which several innovative synthesis methods constitute the basis for the realization of highly controlled nanowires, and we combine this perspective with one of how the different families of nanowires can contribute to applications. One reason for the very intense research in this field is motivated by what they can offer to main-stream semiconductors, by which ultrahigh performing electronic (e.g., transistors) and photonic (e.g., photovoltaics, photodetectors or LEDs) technologies can be merged with silicon and CMOS. Other important aspects, also covered in the review, deals with synthesis methods that can lead to dramatic reduction of cost of fabrication and opportunities for up-scaling to mass production methods.

CONTENTS 1. Introduction 2. III−V Nanowire Growth and Devices 2.1. III−V Nanowire Growth Methods 2.1.1. Au-Seeded Growth 2.1.2. Self-Seeded Growth 2.1.3. Selective Area Growth 2.2. Important Technologies for Nanowire Growth When Fabricating Devices 2.2.1. Patterning 2.2.2. Doping Evaluation 2.2.3. In Situ Measurements 2.2.4. Aerotaxy Nanowire Growth 2.3. III−V Nanowire Devices 2.3.1. III−V Nanowire Transistors 2.3.2. III−V Nanowire Photodetectors and LEDs 2.3.3. III−V Nanowire Photovoltaics 3. III-Nitride Nanowire Materials and Devices 3.1. III-Nitride Material Properties from Growth of Bulk and Planar Structures 3.2. Synthesis of GaN Nanowires and Related Device Applications 3.2.1. Growth Seeded by Metal Nanoparticles 3.2.2. Self-Organized Growth 3.2.3. Selective-Area Growth 3.2.4. Top-Down Synthesis Method 4. Outlook 4.1. Trends in Technology and Cost 4.2. Trends in Novel Application Opportunities Author Information Corresponding Authors ORCID Notes © XXXX American Chemical Society

Biographies Acknowledgments References

A B B B D G

AH AI AI

1. INTRODUCTION The approach to bottom-up creation of semiconductor nanowires (NWs) has opened completely new avenues for nanofabrication and the design and realization of various kinds of devices. This review is covering different kinds of compound semiconductor NWs, in terms of materials compositions and means of NW growth, as well as an overview of some of the most important application areas for such NW materials. In spite of the breadth of this approach, we still limit ourselves to the compound semiconductor systems, in terms of III−V semiconductors, such as InAs, InP, GaAs, GaP, InSb, and GaSb and alloys thereof, and the family of III-nitrides, such as GaN, InN, and AlN, also here including alloys of these binary constituents. The early historical background to NWs stems from the 1960s, when scientists at Bell laboratories demonstrated that, not nano- but millimeter-sized, rods of silicon could be formed via the addition of a gold particle to a silicon wafer with its surface typically oriented in the ⟨111⟩-direction.1 It was shown that as the temperature was increased, while a siliconcontaining precursor gas was added, a eutectic alloy between gold and silicon was formed on the wafer surface. As more silicon was added via the gas phase, the supersaturation of the alloy led to the deposition of excess silicon at the interface

H H H I I J J P R V V W X Y AA AF AF AG AH AH AH AH AH

Special Issue: 1D Nanomaterials/Nanowires Received: January 31, 2019

A

DOI: 10.1021/acs.chemrev.9b00075 Chem. Rev. XXXX, XXX, XXX−XXX

Chemical Reviews

Review

opening for the marriage of ideal silicon-based electronics and III−V NW photonic devices. We will in this review focus on research published in the past five years in order to give an up-to-date status of the field, but we also include older research when necessary to explain how the field has evolved. We will start by reviewing the growth and devices from traditional III−V NW materials, after which we will turn our attention to the III-nitride system. We will finish with an outlook on how we believe the field will develop further in the coming years.

between the Au−Si droplet and the substrate, leading to a monolithic rod of silicon being formed on, and perpendicular to, the wafer surface. This mechanism was given the name vapor−liquid−solid (VLS) growth mode. Obviously, this was neither “nano” nor compound semiconductors. For this to happen, it took at least two decades where, first Givargizov reported studies of VLS growth of compound semiconductors,2 and later a research team at Hitachi Central Research Lab outside Tokyo, under the leadership of Dr. Kenji Hiruma, demonstrated that whiskers, as they called them, of III−Vs such as InAs and GaAs could be nucleated and grown with diameters below 100 nm. This effort included the successful demonstration of functional light-emitting devices in GaAs NWs3 as well as the first realization of heterostructures, as demonstrated with combinations of InAs and GaAs.4 Approximately 10 years after the initiation of the NW technology in Japan, groups at Harvard University (Lieber),5 at UC Berkeley (Yang),6 and our own group (Samuelson)7 started major efforts developing materials science of NW growth as well as demonstrated various kinds of device based on NW structures. Very many research efforts worldwide have since then been added, making this one of the most dynamically developed areas of nanoscience and nanotechnology. A major motivation for the approach of fabricating NWs originates from the inherent advantages of self-assembly, by which the NWs form without any top-down treatment or processing, hence with potentially much more ideal and unaffected surface and materials properties. The methods most commonly used for NW synthesis can be separated into either seed particle assisted (where the seed often is liquid), often referred to as VLS growth, or selective area growth, where growth rate differences between different crystal facets is used. We will here also cover a novel and radically different approach to growth of NWs, as growth in the aerosol phase, with no substrate used to control nucleation and growth, but with only the seed particle inducing a spontaneously induced controlled orientation of the axial NW formation. Radial growth, on the other hand, is readily incorporated typically in a second step of growth, in which the originally grown NW serves as a singlecrystalline substrate for the radial growth of materials, either as part of the device structure or simply for passivation purposes. The very rapid development of the field of NWs has been driven by the ability to directly form various categories of device structures, for instance, quasi-one-dimensional electronic devices, such as diodes and transistors, including tunneling devices, or photonic devices for the emission or detection of light. Most of these families of device applications rely on the controlled formation of heterostructures, meaning the combination of different materials with, ideally, atomically sharp interfaces. In this aspect lies one of the key strengths of the NW approach in the sense that for narrow NWs it has been shown that also materials combinations, having large difference in atomic spacing, can be combined thanks to the very efficient radial relaxation of the strain induced by the lattice mismatch at the interface between the different materials segments. By comparison for traditional, planar growth of such mismatched heterostructures, misfit dislocation forms that ruin the properties of the grown material. Enabled again by the small dimensions of the NWs, the compound semiconductor materials and the unique and superior electronic and photonic devices can often be directly integrated with silicon, hence

2. III−V NANOWIRE GROWTH AND DEVICES In this section, we will review recent advances of III−V NW growth and devices covering the period 2014−2018. We will start out by reviewing the advancements in bottom-up Auseeded, self-seeded, and selective area NW growth. After the growth methods, we will review technologies important for III−V NW growth, especially when they should be incorporated in large area devices, which include techniques to fabricate patterned NW arrays, evaluate carrier concentrations, in situ measurements of the NW growth, and mass production of NWs with the Aerotaxy method. Then, we will give an overall picture of the recent status in what we believe constitute the NW applications that are creating a big impact in each particular field, namely electronics (transistors), light photodetection, and photovoltaics. 2.1. III−V Nanowire Growth Methods

Formation of 1-D nanoscale structures or NWs can be accomplished in two fundamental ways. First, the top-down approach, which relies on having a bulk starting material of high quality, from where it is possible to selectively etch material away and shape the final structure. For this technique to be useful, it is important that there is an added benefit of turning the bulk material into a 1-D structure which results in added functionality of the produced material. In addition, the impact of etching on exposed surfaces is important to handle because otherwise etch damage could decrease the intrinsic material quality. There are several examples in literature where the top-down approach has been successfully used to produce NW structures which enhance the performance of devices8,9 and can show new functionality.10 This technique is, however, limited by that only materials and material combinations which already exist in bulk form can be used. Second, the bottom-up approach, which relies on a disordered starting material that is assembled, or grown, by supplying the right conditions, such as reactants, temperature, and pressure. By assembling the NW without relying on a bulk starting material, it is possible to grow materials and material combinations that are difficult or impossible to form in bulk. A key challenge instead becomes to assemble the material in the correct position on your substrate, with the desired size, shape, and material quality needed for the intended application. This section will deal with NWs produced by the bottom-up technique, including Au-seeded, self-seeded, and selective area growth techniques. We will for each growth method cover the areas of NW nucleation, doping, and heterostructures, which are critical for the electronic and optoelectronic devices covered later. 2.1.1. Au-Seeded Growth. The use of a metal seed to form an elongated semiconductor crystal now stretches back more than 50 years. The original works on both microwires by Wagner, Ellis, and Barnes1,11 in the 1960s and NWs by Hiruma B


Chemical Reviews

Review

et.al12−14 in the 1990s included the use of metal seed particles. The technique is often referred to as VLS describing the three phases present. The role of the metal seed particle is to provide a location where the growth rate is locally enhanced. Our current understanding of why the growth rate is enhanced can be found in refs 2 and 15−17. In short, the enhancement in growth rate can be explained by a reduced nucleation barrier underneath the seed particle compared to the substrate and NW side facets. These models can also be applied to selfseeded NW growth. which we will discuss later. In situ TEM studies have also confirmed that metal particle seeded NWs form one atomic layer at a time from individual nucleation events.18−20 Because of the wide process parameter space available for growth of Au seeded NWs, it has been possible to use both molecular beam epitaxy (MBE) and metal−organic vapor phase epitaxy (MOVPE) to grow and control such NW structures. 2.1.1.1. Seed Particle Material. An important research area for metal seeded NW growth is to understand which seed particle materials that can be used to grow controlled NW structures and why some seed materials are more favorable than others. So far Au has been the most used seed material for growth of III−V NWs. However, there are several aspects one needs to consider when choosing a seed material. These include the materials resistance to oxidation, its ability to form alloys with the semiconductor materials to be grown, melting temperature, possibility to form nanoparticles with a controlled size, potential risks for incorporation of the seed material as impurities inside the NW, and, of course, cost, if scalability is important. Several materials have been explored besides Au in recent years such as Ag,21,22 Cu,23 Ni,24,25 and Sn.26 Although some of these have shown great promise, their use in large area devices has so far been limited. We will therefore focus on developments with Au because this material offers an excellent test bed to show the possibilities with NWs structures. We refer interested readers to a review by Caroff et al.,27 which extensively covers different seed materials. 2.1.1.2. General Growth Conditions for Au-Seeded Nanowires. Next, we will give a general introduction to growth of Au-seeded NWs, after which we will dig deeper into nucleation, heterostructures and doping, which are relevant for device applications. Nanowire growth seeded by Au particles has shown a remarkably wide process parameter space with growth temperatures ranging from 350 to 700 °C and V/III ratios from below 1 to several thousands. This versatility has proven important when the properties of the NW structure should be tuned in terms of crystal structure, shape, conductivity, and material composition. However, typically, the growth takes place at lower growth temperatures than used for the same materials in bulk layer growth. This is to ensure kinetically limited growth conditions on the NW side facets and growth substrate, which limits their growth rate. In this way, it is easier to control the NW properties than if both axial (underneath the seed particle) and radial (on the NW side facets) growth takes place at the same time. Simultaneous axial and radial growth can lead to crystal defects,28,29 inhomogeneous dopant incorporation,30 and carbon impurities.28,29 Several techniques have been developed to avoid unwanted radial growth, which include in situ etching with HCl and HBr,28,31,32 tuning the crystal structure,33−36 and lowering the growth temperature.37 2.1.1.3. Au-Seeded Nanowire Nucleation and Growth Direction. Above, we gave a general description of Au seeded

NW growth, and using this as our starting point, we will in the following section cover how the particle interacts with the substrate during nucleation and which role this has in determining the NW growth direction. When initiating NW growth, the Au particles are typically in contact with a crystalline surface unless a substrate-free technique such as Aerotaxy,38 or a noncrystalline substrate such as quartz, is used. The interplay between the substrate and the seed particle determines in which direction the growth will take place, i.e., if growth will proceed perpendicular to the substrate surface at a nonperpendicular angle or in the substrate surface plane.39 If no epitaxial substrate is present, a crystal nuclei has to form at the Au particle surface, from which the growth can proceed. In this process, the driving force for growth in the ⟨111⟩ direction is very strong, and as an example, more than 99% of Aerotaxy NWs grow in this direction even though there is no epitaxial substrate to guide the growth.38 When nucleating on a crystalline surface, using a (111)B substrate, is by far the most common approach. By using another substrate such as (001) instead, one can however achieve better control of the NW crystal structure at the same time as the process becomes more transferrable to industry standard (001) substrates.40−42 To achieve vertical growth on a non-(111)B substrate, it is important to suppress the formation of the (111)B facet underneath the seed particle and tune the seed particle composition (see Figure 1a−d).43 The trade-off when nucleating on a (001) substrate thus becomes a more limited process parameter space. Although growth perpendicular to the substrate is the most popular choice when fabricating devices which contain many NWs, engineering the growth direction opens up new possibilities. By changing the growth direction during the growth process,43,44 it is for example possible to create crossed NW junction structures which could find future uses in quantum computing (see Figure 1e−h).45,46 2.1.1.4. Au-Seeded Nanowire Heterostructures. After describing nucleation and NW growth directions above, we next turn to the formation of heterostructures and tunable alloy structures, both in the axial and radial directions. The axial NW heterostructure has been regarded as one of the key benefits of NWs compared to planar layers because strain can be elastically relaxed via the free surfaces, thus reducing defects such as dislocations when there is a lattice mismatch. Although the flexibility even for axial heterostructures is not endless and misfit dislocations eventually will form,47 there are unique possibilities for new defect-free material combinations compared to planar growth such as InAs-InSb,47 GaAsGaSb,47 InAs-GaSb,48 GaAs-InAs,49 GaAs-InGaAs,50 InPInGaP,51 GaP-InGaP,52 and InAsP-InP.7,53,54 The main purposes for growing these heterostructures ranges from creating a transition from a substrate material into a desired active device material,48 creating an active part of a device by promoting tunnelling at a staggered bandgap heterostructure interface55 or for creating quantized structures used in for example infrared photodetectors (see Figure 1i−m).53,54,56 However, when growing ternary alloy materials such as InxGa1−xAs and InxGa1−xP, where alloy mixing occurs on the group III sublattice, it is important to consider the implications the growth will have on the full 3-D NW structure. For example, it has been observed that composition can vary in the axial51,52 as well as the radial direction35 due to the difference in group III adatom diffusion lengths. This leads us in to the topic of radial heterostructures and how to control these. The most common use for a radial heterostructure in Au-seeded C


Chemical Reviews

Review

Figure 1. (a−d) Nucleation optimization of InP NWs on a (001) substrate where the yield is optimized by adding TMIn, which changes the seed particle composition before growth is initiated. Scale bars are 5 μm.43 (e−g) Fabrication of crossed NW junctions of InSb grown on an InP stem by deliberately inducing a kink from a ⟨001⟩ to ⟨111⟩ B growth direction. The Au particle positions are optimized to favor crossed junctions. Scale bars are 200 nm.45 (h) Crossed InP-InSb NW junctions grown by initiating growth in V-grooves with a (111) surface on a (001) substrate. Scale bar is 1 μm.46 (i) An InAs (blue)−InSb (red) heterostructure where growth of the InSb segment has been suppressed on InAs NWs with smaller diameter.48 (j−m) SEM of array of InP NWs along with HAADF-STEM and EDX linescans showing 20 embedded InAsP quantum disc structures showing PL in the 1.0−1.2 eV region. Scale bar is 1 μm in the SEM image and 200 nm in the HAADF-STEM image.56 (a−d) Adapted with permission from ref 43. Copyright 2013 American Chemical Society. (e−g) Adapted with permission from ref45. Copyright 2014 John Wiley and Sons. (h) Adapted with permission from ref 46. Copyright 2017 Springer Nature. (i) Adapted with permission from ref 48. Copyright 2015 American Chemical Society. (j−m) Adapted with permission from ref 56. Copyright 2017 American Chemical Society.

NWs is to employ it as a surface passivation.35,57,58 One cause for the more limited use of radial heterostructures for Auseeded NWs could be the interference of the Au particle during the shell growth step. This seems to be more severe for shells containing In, where growth underneath the Au can be considerable during the shell growth step,34,59 compared to, for example, AlGaAs shells.58,60 One possibility to circumvent this is to remove the Au particle by for example a wet etch procedure outside of the growth reactor between the core and shell growth steps.61,62 2.1.1.5. Doping of Au Seeded Nanowires. To provide insight into the dynamics when dopants are used in the NW growth process, there has been studies done on core−shell growth,63 doping of ternary InGaP NWs,64 the effect of group III precursor flow on doping concentration,65 and the switching dynamics between intrinsic and doped material.66 In these studies, complex processes involving the decomposition and diffusion of different growth species in the vapor phase on the NW surfaces and in the Au particle have been found to affect the homogeneity of carrier concentration, material composition, and doping profile abruptness. One goal of these doping studies has been to more reliably incorporate doping in p−n junctions that can be used in for example photovoltaic and light emitting devices where it is critical to control the doping profile.57,67−69

2.1.2. Self-Seeded Growth. In the following section, we will outline the most important aspects of the self-seeded growth technique. We will start with a general background, after which we will cover the topics of nucleation, heterostructures, and doping. The self-seeded growth mechanism relies on using the low melting temperature group III element as a seed for the NW growth. This provides several benefits over the Au seeded growth because no impurities are expected to be incorporated from the seed, and the seed can also be consumed if one wants to change growth mode from axial to radial.70 MBE is so far the most commonly used growth technique for self-seeded NWs although MOVPE has been used to some extent. Recently, the materials grown by the self-seeded technique using Ga seed particles includes GaAs,41,71−74 GaP,75,76 GaAsP,77−79 and GaAs1Sb1−x,80,81 while In seed particles have been used to grow InAs82 and InP.83−86 2.1.2.1. Self-Seeded Nanowire Nucleation. Self-seeded NWs can be nucleated on both native73,87 and non III−V substrates such as Si.72,88,89 In the literature, several different techniques for successful nucleation can be found. We will here focus on the investigations of Ga seeded GaAs NWs because several extensive nucleation experiments have been reported and these NWs have also been employed in devices. The nucleation of Ga seeded GaAs NWs includes the use of an oxide to promote nucleation both on GaAs and Si D


Chemical Reviews

Review

Figure 2. (a,b) GaAs NWs seeded by Ga droplets grown on an Si substrate with a 95% yield. The scale bar corresponds to 200 nm.91 (c−f) Highangle annular dark field STEM images and schematic of a radial GaAs-AlGaAs multishell structure where Al poor quantum dot structures are formed in the ⟨121⟩ corners of the AlGaAs shells.93 (g,h) Al composition profiles and HAADF-STEM image of a self-seeded GaAs NW with AlGaAs insertions grown for different time periods. Scale bar is 0.5 μm in h.96 (i−k) SEM and HAADF-STEM image of self-seeded GaAs NWs with axial GaAsP insertions. Scale bar is 500 nm in (k).95 (a,b) Adapted with permission from ref 91. Copyright 2011 Institute Of Physics. (c−f) Adapted with permission from ref 93. Copyright 2013 Springer Nature. (g,h) Adapted with permission from ref 96. Copyright 2016 American Chemical Society. (i−k) Adapted with permission from ref 95. Copyright 2016 American Chemical Society.

substrates.72,87 For a Si substrate, such an oxide can be either the native, typically used for random nucleation of NWs on the substrate wafer, or thermally grown SiO2, which can be patterned by lithography. For a GaAs substrate, the native oxide is not stable enough at high temperatures and thus a more stable oxide such as SiO2 can be deposited.87 The role of the oxide is to create designated places for Ga droplet formation and subsequent NW growth. When using a native oxide which does not have predefined holes, pin holes are induced due to thermal treatment before the growth.89 Ga adatoms can then be collected in the pinholes and form droplets which are in contact with the crystalline substrate. Similar for a lithographically patterned substrate, Ga adatoms can accumulate in holes defined by lithography and etching. Once the Ga droplet has been formed, the wetting of the droplet with the substrate and oxide and the nucleation of the first layers determine if the NW growth is vertical from the substrate.72,89,90 By optimizing the oxide layer and formation of Ga seed particles, it is possible to achieve up to 95% yield of vertical GaAs NWs on Si (see Figure 2a,b).91 2.1.2.2. Self-Seeded Nanowire Heterostructures. After describing the requirements for nucleation in the previous paragraph, we will next turn to the formation of heterostructures. Historically, there has been a large interest to investigate radial heterostructures of self-seeded NWs. This is most likely related to the growth mechanism itself because in contrast to Au-seeded NWs the seed particle can be consumed in situ, and radial growth can thus be promoted. This in combination with the MBE growth technique has led to development of impressive core−shell structures of primarily GaAs-AlxGa1−xAs, where multishell structures have been

grown.92 During growth of the AlxGa1−xAs shells, it has been observed that the Ga and Al compositions are inhomogeneous due to their difference in adatom mobility on the NW side facets.93 Because of the localization of Al poor material inside the shell, quantum dot emitters can be realized with line widths below 100 μeV (see Figure 2c−f).93,94 In recent years, there has also been a growing interest in axial heterostructures. This includes axial heterostructures, where either the group V atom is switched in GaAs-GaP75,95 and GaAs-GaAs1−xSbx,81 or the group III atom is switched in GaAs-AlGaAs.96 Because the seed droplet consists of the group III material, a switch on the group V sublattice has a larger potential especially for realizing sandwich structures such as GaAs-GaP-GaAs because the seed droplet then can be kept intact during the heterostructure formation. Harmand et al.75 have showed that by tuning the switching sequence between P and As sources it was possible to change the P content from 28% to 85% and to transition from GaP to GaAs within 2 MLs. Importantly, they also demonstrated the possibility to go from GaAs to GaP and back to GaAs, effectively creating an electron barrier inside the NW (see Figure 2i−k). When instead trying to switch material on the group III sublattice, one faces the problem that either the seed particle has to be replaced if one wants to switch material from one binary to another, such as InAs to GaAs,97 or it will only be possible to reach a certain threshold alloy composition where the seed particle is still stable. Again, Harmand et al.96 have shown that it is possible to switch from GaAs to AlxGa1−xAs and back to GaAs by dissolving Al in the Ga seed particle. By optimizing the growth sequence, it was possible to achieve Al concentrations of above 50% in the AlxGa1−xAs segments (see Figure 2 g,h). E


Chemical Reviews

Review

Figure 3. (a,b) Study of nucleation of selective area grown GaAs NW on different substrates at two different nucleation conditions which favors either growth in the ⟨111⟩ or ⟨110⟩ direction.122 (c−h) SEM images and schematic of the TASE growth process where a hollow SiO2 tube is used to guide growth of III−V material on substrates with different crystallographic directions.126 (i,j) Axial GaAs-GaAsP heterostructure in a selective area grown NW.130 (k,l) False colored SEM images showing micro-PL mapping of dopant concentration in selective area grown InP NWs. The NW in (k) is not intentionally doped, while the NW in (l) has been intentionally doped with Si.137 (a,b) Adapted with permission from ref 122. Copyright 2007 Elsevier. (c−h) Adapted with permission from ref 126. Copyright 2014 American Chemical Society. (i,j) Adapted with permission from ref 130. Copyright 2014 American Chemical Society. (k,l) Adapted with permission from ref 137. Copyright 2015 American Chemical Society.

2.1.2.3. Doping of Self-Seeded Nanowires. Next, we will focus on the doping studies published for NWs grown by the self-seeded technique. The main part of doping studies currently exists for Ga seeded GaAs NWs, which are typically grown by MBE. Here, the most common dopants are Si,98,99 C,99 Be,70 and Te.70 Even though the self-assisted growth process is more sensitive than Au-seeded, due to the intricate balance needed to sustain the seed droplet, the use of both Be and Te dopants has given limited effects on the NW morphology.100 Interestingly, it has been found that Be can

incorporate preferentially on certain facets which are available underneath the seed particle during the NW growth.101 This adds additional challenges when optimizing core−shell doping profiles which can be very sensitive to the doping level.102 Furthermore, it has been shown that the vapor−solid growth of Te-doped shells can have order of magnitude lower carrier concentration than simultaneous growth on planar layers.100 An interesting approach to achieve doping but at the same time maintain high material quality and carrier lifetimes is to employ modulation doped core−shell structures.103 The core− F


Chemical Reviews

Review

axial to radial growth by simply tuning the growth parameters. With the selective area growth technique, it is similar to the previously mentioned techniques, possible to grow the NWs on a Si substrate. This has been done for primarily the Asbased materials InAs, InGaAs, and GaAs with vertical NW yields ranging from 95 to 100%.123,124 The key to achieve high yields and thus controlled growth is to completely remove oxide residues from the Si surface inside the holes in the growth mask and to terminate the Si (111) surface with As and thus form a (111)B type surface before growth is initiated. This procedure has also been applied to the growth of InAs NWs on Ge.125 To grow vertically oriented selective area NWs on substrates other than (111), it is possible to employ an oxide template tube which restricts the growth direction. This template assisted selective area (TASE) technique has been used to successfully grow vertical III−V NWs on Si (100), (110), (112), and (111) substrates (see Figure 3c−h).126 In addition, also growth on silicon-on-insulator (SOI) substrates is possible which can be used for on-chip optical communication.127 2.1.3.2. Selective Area Nanowire Heterostructures. After describing the nucleation and growth mechanism in the previous section, we will next describe the formation of heterostructures in the actual NW structure. As has been discussed for both Au-seeded and self-seeded NWs, there are two main types of heterostructures: axial formed in the growth direction of the NW and radial where a core−shell structure is grown. Similar to the self-seeded technique, radial heterostructures has historically been most widely employed for selective area NWs, but in recent years there have been several advances in terms of axial heterostructures. The main limitations for growth of axial heterostructures are the difficulties in avoiding simultaneous radial growth as the axial segment is formed and to achieve sufficient composition tunability. There are, however, reports of axial heterostructures of GaAs-InGaAs,128 GaAs-AlGaAs,129 and GaAs-GaAsP,130 where the axial segment has been kept sufficiently short to avoid growth on the NW side facets (see Figure 3i,j). To avoid the radial growth, it is, however, also possible to use the TASE technique, described previously, where the oxide tube protects the NWs sidewalls from deposition.131 Core−shell heterostructures have been used for surface passivation,132 core to shell crystal structure transfer,133 nanotube formation,134 and to form active layers inside NW transistor devices.135 2.1.3.3. Doping of Selective Area Nanowires. Next, we will focus on the area of doping in selective area NWs. Selective area has some potential benefits for controlling the doping profile compared to Au-seeded and self-seeded NWs, because there is no seed particle that can store the dopant atoms and give a carry-over effect between different doped segments. Interestingly enough, there exist several reports of both axial and core−shell p−n junction devices demonstrating the flexibility of the growth technique. The growth can, however, be significantly affected by dopants, which can change the ratio between growth rates in the axial and radial growth directions.136 Quantitative studies have been performed on both InP137 (see Figure 3k,l) and GaAs138 NWs using Si as the dopant. These have shown that the doping level was tunable over roughly 1 order of magnitude for both materials by changing the dopant flow. Even though quantitative studies of doping levels in selective area NWs are scarce, it has not stopped the successful implementation of dopants in numerous

shell p−n junction is the most commonly reported device geometry for self-seeded NWs and has been used to fabricate both photovoltaic (PV)70 and light-emitting diode devices (LED).104 There are several promising aspects for incorporating core−shell devices using the self-seeded technique because it has been shown that the shell growth can be controlled with high precision. This can for instance make it possible to create multiple heterostructures within the p−n junction structure, thus optimizing the band structure in for example LED devices. 2.1.3. Selective Area Growth. We will in the following section outline the most important aspects of selective area growth (SA). As with the other growth techniques discussed above, we will start by a general background after which we will focus on nucleation, heterostructures, and doping. Selective area growth of NWs is most commonly done with MOVPE. It uses an inert mask template to define specific positions on a substrate where epitaxial growth can take place. Contrary to Au-seeded and self-seeded growth techniques, the growth often takes place at similar growth temperatures as for 2-D layers. The growth technique itself was developed as early as the 1960s, when structures considerably larger than NWs were grown.105 The growth technique was later further refined, which made it possible to grow novel laser106 and transistor structures,107 where heterostructures were incorporated. In the late 1990s, the dimension of the openings in the inert growth mask were decreased and thus the selective area growth technique was used for the first time to produce NW structures, and as small as 53 nm GaAs pillars were reported.108 The field of NW growth using selective area was advanced significantly by the research group led by Fukui in the 2000s and materials such as GaAs,109 InAs,110 InP,111 and InGaAs112 were grown. Later, other groups also grew materials such as InGaP,113,114 AlInP,115 InAsSb,116 and InAsP.117 In recent years, several groups who traditionally worked on particle seeded NW growth have also started to employ the selective area technique, especially to grow wurtzite InP NWs.115,118−120 2.1.3.1. Selective Area Nanowire Nucleation and Growth Mechanism. After the general introduction given above, we will now turn our focus to the nucleation and growth mechanism of selective area NWs. All NW materials listed above have been reported to grow in the ⟨111⟩ B direction, except for InP and InGaP which preferentially grow in the ⟨111⟩ A direction. A possible explanation for the difference in growth direction for the InP-based materials is that the formation of P-trimers on the P-terminated (111)B surface hinders the incorporation of In on this surface. The (111)-A surface on the contrary is instead In-terminated and thus does not suffer from this problem.121 The selective area NW growth itself relies on the formation of low index facets which grow at different rates. Regardless of the substrate used, the (111)B, (111)A, and {110} family of facets tend to appear (see Figure 3a,b). This means that these facets grow slower than other facets such as (001) and will thus be the facets defining the NW structure.122 Because of the orthogonal symmetry between the (111)A/B and {110} planes, growth on a (111)A or B substrate in mask openings will produce a wire structure bound by a top (111)A or B facet and six {110} facets. The growth rate between the (111) and {110} facets can itself also be tuned by adjusting growth conditions. By using a high (low) growth temperature and low (high) group V partial pressure, the growth rate in the ⟨111⟩-direction (⟨110⟩direction) is promoted.122 Thus, it is possible to switch from G


Chemical Reviews

Review

Figure 4. Process optimization of NIL patterns for Au seeded growth. (a−d) Example of a NIL defined pattern which has been optimized by adding a piranha etch prior to growth to remove unwanted residues from the lithographic step. The residues caused growth of smaller wires, seen in (b) and also changed the NW morphology.143 (e−h) Top view SEM images which show an example of how an added nucleation step, where the group III precursor is introduced before a high temperature annealing step can increase the pattern fidelity of a NIL pattern. The group III precursor was introduced at a temperature of 320 °C in (e), 360 °C (f), or 420 °C (g)147 (a−d) Adapted with permission from ref 143. Copyright 2010 Institute Of Physics. (e−h) Adapted with permission from ref 147. Copyright 2016 Springer Nature.

devices ranging from photovoltaics124,132,139 to LEDs130 and transistors.125,140

patterns can be fabricated with high resolution. Because of its sequential nature, it is, however, quite slow if larger volumes of high density patterns is required. In recent years, there has therefore been a significant increase in the use of nanoimprint lithography (NIL) to define large-area patterns with a high throughput. NIL has been used with excellent results for Auseeded, 142,143 self-seeded, 144 and selective area NW growth.120,145,146 Because of the parallel nature of NIL, large area patterns on for example 2” wafers can be made with relative ease. The drawback is that there is no versatility in the pattern, and every pattern requires a specific stamp, which can be expensive to fabricate. The use of NIL when growing NWs for photovoltaic application has been one of the key components to achieve high efficiencies. Using NIL, it has been possible to fabricate NW arrays with the correct diameter and spacing for maximized light absorption in large volumes, which enabled a rapid development of NWs with uniform properties.29,57,67,68 The use of lithographic techniques can, however, also cause issues with for example surface cleanliness143 and seed particle movement.147,148 These challenges can nonetheless often be overcome by, for example, choosing suitable materials in the lithography process and/or introducing extra nucleation steps in the NW growth procedure (see Figure 4). 2.2.2. Doping Evaluation. Doping evaluation is important to use when the NW structure should be used for electronic or optoelectronic applications. We will here focus on the most commonly applied techniques developed for III−V NWs in the past five years and for more doping characterization techniques not covered, here we refer to a review by Wallentin et al.149 In recent years, a large number of techniques have been developed or evaluated to quantify carrier concentration or doping atom concentration in NWs. These include the Hall effect,63,150−153 photoluminescence (PL),153−155 cathodoluminecence,98,153 Raman spectroscopy,100 thermoelectric measurements,156 photoconductivity measurements with terahertz spectropscopy,99 electron holography,157 nanobeam X-ray fluorescence,66 secondary ion mass spectrometry (SIMS,)158 and atom probe tomography.159 These techniques can

2.2. Important Technologies for Nanowire Growth When Fabricating Devices

After discussing the fundamental growth techniques in the previous section, we will next focus on important aspects when NWs are incorporated in vertical devices with potential use in industrial applications. In recent years, there has been significant development of NWs, which are incorporated in array devices containing millions of NWs. This is necessary to create large area devices which are useful for many applications. This sets new requirements on the NW growth process beyond just optimizing each individual NW structure. Now, the challenge becomes to fabricate and control shape, size, and position of millions, or even billions, of NWs so that they all have the same properties and thus can give reliable and reproducible device characteristics. In addition also, the NW growth method has to provide a viable alternative in terms of cost. We will deal with the advancement in the four key areas of patterning, doping evaluation, in situ measurements, and high volume Aerotaxy NW growth in the following sections. The patterning and characterization techniques are general and can be applied to NWs grown by any of the different techniques outlined previously. 2.2.1. Patterning. By using lithographic patterning, it is possible to design a NW array by means of controlling the location of NW formation with high precision. This is a key enabler to achieve reproducible and uniform growth results, and in this way the surrounding area of each NW can be the same. Because the NW growth rate is most often limited by material supply, NW to NW equidistance ensures an identical growth rate for different NWs within an array and results in a smaller spread of other NW properties such as doping, crystal structure, and material composition. All of these parameters are critical to control if the NWs should be part of a larger area vertical device. Electron beam lithography is the most widely used technique to define nanoscale patterns and has been used to define patterns for Au-seeded,141 self-seeded,91 and selective area NWs.112 This technique is very versatile, and most H


Chemical Reviews

Review

Figure 5. Schematic of a multistage Aerotaxy system for growth of GaAs NWs with an axial p−n junction consisting of (a) metal (Au) particle generation, (b) compaction of nanoparticles in a sinter furnace, (c) nanoparticle size selection in a differential mobility analyzer, (d) alloying stage, (e) p-type growth stage, (f) nominally intrinsic growth stage, (g) n-type growth stage, and (h) NW deposition.69 Reproduced with permission from ref 69. Copyright 2018 American Chemical Society.

complement previously developed techniques such as field effect measurements 160 and provide a more accurate description of the NWs electrical properties. One important step toward making the measurements more reliable has been to compare and benchmark different techniques against each other. This has been done for Raman spectroscopy together with PL, SIMS, and electron holography,100 Hall effect with optical techniques,153,161 and Hall effect with traditional fieldeffect measurements.151 Besides the reliability of the quantification of the carrier concentration also the spatial resolution of the measurement is important because the carrier concentration can vary significantly along the axial and radial directions of the NW.137,150,159 Of the previously mentioned techniques Hall effect (∼300 nm resolution), micro-PL (∼300 nm resolution), cathodeluminescence (∼70 nm, limited by carrier diffusion length), electron holography (∼1 nm resolution), nanobeam X-ray fluorescence (∼50 nm resolution), SIMS (∼1 nm in z-direction), and atom tomography (∼0.2 nm) provide spatial resolution and make it possible to determine either the carrier concentration or dopant atom concentration along the NW length or radius. 2.2.3. In Situ Measurements. In this section, we will describe different ways to monitor NW growth in situ in actual large scale growth systems such as MOVPE and MBE. These techniques can not only provide information about the grown NW structure but also on its evolution and growth dynamics. There are three main techniques which have been used to investigate NW growth in situ, two of which have been used in MBE and one which has been used in MOVPE. Because of the low pressure inside a MBE system, it is possible to use reflection high energy electron diffraction (RHEED). This has been used to study initial stages of growth and the NW crystal structure.162 The low pressure also enables the use of mass spectrometry, which can track the amount of desorbing material from the surface. This information together with the incoming material flux can then be used to determine the growth rate on the substrate.163 In MOVPE, in situ techniques often rely on optical reflectance. Optical reflectance is traditionally used when growing layers with MOVPE to investigate growth rate and surface reconstruction.164,165 When applying this technique to NWs, the measurement of the axial growth rate follows the same principle as for layers. Here, the incoming light, which can be either single wavelength or a

broadband source, is reflected from the substrate surface and the NW top surface.120 The two reflected rays interfere and thereby give rise to an oscillating intensity which depends on the light wavelength, the refractive index of the NW layer, and the NW length. For sparse NW arrays, a wavelength independent refractive index of 1 can be used because the light reflected from the substrate travels between the NWs. However, if a denser array is used, the light interacts with the NW material and a refractive index must be either calculated or measured. Interestingly this optical reflectance technique can also be used to determine the NW diameter in situ. This is possible because NWs exhibit diameter dependent absorption resonances. By tracking one or more absorption resonances and how they shift in wavelength during NW growth, the NW diameter can be deduced.120 This technique has been used to investigate the growth dynamics of crystal structure transitions within NWs as well as the evolution of ternary51,166 and doped64,120 NW structures. 2.2.4. Aerotaxy Nanowire Growth. The progress made on developing III−V NW structures described in the previous sections has relied on the same principles and fabrication equipment as for 2-D layer growth. This has been a large benefit because previous knowledge and growth models from layer growth could be applied or adapted to the growth of these new structures. It has, however, also limited the possibilities that nanotechnology can offer in terms of radically changing how materials are created. This means that III−V NW growth in these systems will carry a similar cost as traditional 2-D layer growth, which will limit the possible application areas. It also means that devices made from NW structures need to have better performance than their corresponding 2-D layer grown structures in order to compete. One way to radically change how single crystalline III−V nanostructures can be grown is to combine a growth reactor with an aerosol system, resulting in an Aerotaxy system (see Figure 5). The aerosol system here supplies size selected metal nanoparticles of for example Au or Ga, which can be used to grow NWs38 or nanoparticles.167 The underlying principle of the fabrication equipment is fundamentally different from a normal MOVPE reactor, although the same precursors are used. Instead of the carrier gas only carrying the precursors to a growth substrate, the nanoparticles, which initiate the crystal growth and thus can be considered as the “substrate”, are also I


Chemical Reviews

Review

suspended in the carrier gas and there mixes with the precursor gases. Because this happens at a controlled and elevated temperature crystal growth is possible. In recent years, the groundwork to create more elaborate structures has been made with investigations of both p-type155 and n-type168 doped NWs. Also, the ability to grow NWs with a tunable bandgap has been demonstrated by growth of different GaAsP alloys.169 A major advance was the realization of the first pn-junction grown completely in the aerosol phase where a four-stage sequential growth system was used (see Figure 5).69 The use of multistage systems is necessary because a single stage has limited capability to produce more than one type of material, and thus more stages are needed when the complexity of the desired nanostructure increases. The Aerotaxy fabrication method of course also creates challenges when, for example, the NWs need to be incorporated into larger area devices that contain many NWs. This requires the NWs to be aligned and stacked before process steps can be applied to form contacts, etc. This has been shown to be already be possible with technology developed by Sol Voltaics AB, which is based in Lund, Sweden.69 We will, however, also address this issue further in our outlook section.

Table 1. Summary of III−V NW-Based Applications That Are Currently Being Developed, Together with Some Recent, Representative References application

reference

transistors photodetectors and LEDs photovoltaics X-ray detection THz detection tunnel junctions photoelectrochemical cell optical interconnects lasers biology gas/chemical sensing thermoelectrics quantum computing

see section 2.3.1) see section 2.3.2) see section 2.3.3) 176 177,178 179−182 183,184 127 85,185−188 189−191 192−194 195,196 197

date review, we hope to draw attention to III−V NW potential and foster even more efforts toward commercially viable NWbased devices. 2.3.1. III−V Nanowire Transistors. Metal-oxide-semiconductor field-effect transistors (MOSFET) constitute the main building block of integrated circuits (IC), and aggressive transistor miniaturization during the last 40 years (fulfilling Moore’s Law prediction) has enabled packaging of billions of transistors in one single IC chip. However, as miniaturization proceeds, challenges such as control of short channel effects and power consumption management need to be addressed. III−V NW-based transistors are promising candidates for beyond Si CMOS technology198,199 and high frequency electronics applications.200 First, III−V semiconductors are ideal as a channel material due to their inherent high mobility values, which increases performance.198 On the other hand, the NW geometry not only offers better electrostatic control by the reduced dimensions and gate-all-around (GAA) configurations, allowing for aggressive scaling, but also enables material bandgap engineering, which yields lower drive voltages while maintaining sufficient on-state current (ION) and reduced offstage leakage currents (IOFF), decreasing power consumption.199,201 The InAs material stands out within the III−V semiconductor family for its direct, narrow energy bandgap (0.354 eV) and high electron mobility (40 × 103 cm2/(V s)), which makes InAs a suitable candidate for transistors.198 In particular, for NW transistors, InAs also shows low contact resistance and sufficient interfacial quality for high-k dielectrics.198 There has recently been a remarkable research effort to develop InAs and In(Ga)As NW n-type transistors, which actually compete nowadays with planar counterparts in terms of key performance parameters. Therefore, in this section we will mainly focus on recent development of In(Ga)As-based NW n-type transistors. In addition, as CMOS circuits also require p-type transistors, there has also been efforts to develop the (In)GaSb material for NW-based p-MOSFETs given its relatively high hole mobility,202 as we will discuss later on. NW transistors have been developed since the early development of NW growth at the beginning of the century,203−206 motivated by the possibility to integrate III− V materials with high mobility values on low-cost Si substrates207,208 and that the NW geometry fulfilled the requirements imposed by transistor downscaling. NW

2.3. III−V Nanowire Devices

In sections 2.1 and 2.2, we showed that understanding and control of III−V NW growth have reached a well-developed stage, where several high quality materials with a large variety of dopants and doping levels can be combined in multiple ways. This development was triggered in part by the ultimate goal of producing devices at the nanoscale. Device miniaturization is justified as long as the trinomial better performance, lower cost, and lower power consumption is considered as a whole170 because these three aspects are often intertwined, although one can argue that all three of them are not always necessary for some specific niche markets. In this respect, III− V NW-based devices exhibit a significant potential for applications in photonics, electronics, and optoelectronics with special usage for specific innovative and diverse markets such as the Internet of things or biomedical applications.171−175 Such potential relies not only on the reduced dimensions and high aspect ratio (i.e., high surface area) of the NWs but also on the inherent and unique advantages of the NW geometry such as optical antenna effect, excellent electrostatic potential control, combination of dissimilar III− V materials, and integration on Si-based platforms. However, III−V NW-based device development not only implies a detailed understanding of material, doping, and junction formation (if needed) as seen in section 2.1) but also a careful device design as well as mastering all the technological steps involved to develop a full working device (e.g., gate dielectrics, electrical contacts, etc.), especially when integrating an array of millions of vertical NWs. III−V NW-based devices have attracted much attention worldwide in recent years, which has turned into a rapidly evolving field. Indeed, Table 1 summarizes a selection of applications, together with some recent representative references, that are currently being developed. However, this section will only focus on the recent development in the four NW applications that are creating a big impact in each particular field, namely electronics (transistors), light photodetection, light emission (LEDs), and photovoltaics. For more in-depth reviews in each field, the reader is referred to more specific reviews indicated in each subsection. With this up-toJ


InAsf

Abbreviations: MOVPE = metalorganic vapor phase epitaxy, SA = selective area, Au = gold catalyzed, NA = not available, VG-VI = vertically grown and integrated, VG-HI = vertically grown but horizontally integrated, HG-HI = horizontally grown and integrated, d = diameter, W/H = width/height, ION = on current, IOFF = off current, SS = subthreshold swing, Vds = drain to source voltage, LG = gate length, gm = transconductance, DIBL = drain induced barrier lowering, Ron = on-resistance, EOT = equivalent oxide thickness, Q = Q-factor, ref = reference. bNormalized to the NW circumference. c Vds = 0.5 V. dIOFF 100 nA/μm, Vdd = 0.5 V. e1 μA/μm. fReported gm, SS, ION do not belong to the same wire, i.e., maximum or minimum values measured among many NW devices.

266 1 VG-HI NA

HG-HI InP

MOVPE, SA MOVPE, Au In0.85Ga0.15As

transistors have been demonstrated both in the vertical and horizontal (lateral) geometry.199,210−212 Vertically aligned NW transistors reduce transistor footprint, enabling complex 3D integration approaches, and lower power consumption for scaled digital devices is expected.126,213−215 In addition, the transistor footprint gets decoupled from gate length,216 which yields a higher transistor density with lithography-independent gate length definition and core-multishell structures can be realized.135 However, processing of such vertically aligned transistors is a rather complex technological process. Even though single devices and smaller circuits have been demonstrated,126,209,217 a sufficiently high yield for large scale integrated circuits has not yet been achieved. On the other hand, NWs in the horizontal geometry enable coplanar integration with Si CMOS devices218 although additional processing is needed to optimize gate-channel coupling by a full GAA configuration.219−223 Importantly, a special effort has been made in developing NW transistors compatible with Si-based transistor semiconductor industry, which has been proven with direct NW growth on Si by TASE,126,218 SA,135 or NW growth on InAs buffer layers on Si.224 Other significant developments include integration of III−V NWs on a Ge substrate for combined III− V/Ge hybrid CMOS architectures.125 To prove the potential of III−V NW transistors and stimulate further advancement in the field, several circuits and applications based on InAs NW transistors have been reported recently. CMOS logic gates based on cointegration of InAs and InAs/GaSb NWs on Si,48,209 as well as track and hold circuits213 and RF down-conversion mixers,225 have been demonstrated. In addition, InAs NW transistors were proposed as gas sensors226 and recent reports continue expanding this field,192,193 including detection of charged chemical and biological species.194 Next, we will focus on recent developments of two particular transistor technologies, namely MOSFETs and tunnel field effect transistors (TFET). Since the first demonstration of a vertical III−V NW transistor in 2006,205 we have witnessed an impressive development in NW MOSFET technology, with record performances of NW-based transistors even outperforming Si-based counterparts.227 On the other hand, the NW geometry is playing a significant role in TFET development as it benefits from bandgap engineering, which constitutes a significant advantage with respect to other technologies. Following the same approach as in section 2 devoted to growth methods, here we will only include recently reported results of NW FETs made with grown NWs (e.g., bottom-up or TASE growth), although some impressive results based on a top-down approach228−231 or replacement fin process technique232,233 have been reported as well. 2.3.1.1. Nanowire Metal-Oxide-Semiconductor FieldEffect Transistors. In the last five years, there has been a prolific amount of InAs-based MOSFET devices reported,125,208,209,216−218,220−222,227,234−242 with around 10 research groups active worldwide in the field. Recent reviews can be found in refs 199,200,208,211,243, and 244. Importantly, the first reports on devices made of more than 1 NW are starting to be published216,218 and the RF performance is gaining momentum.200,238,245−247 We identify NW diameter, sidewall roughness, and gate stack quality as key aspects that have attracted attention in these years (and will continue to do so) as well as enabled

a

234 2016 NA NA 314 >20 130 2.693 0.84

227 45

2017

2016 340 175 290 65 NA 650 138 66 2.40 3

cylindrical, d = 37 nm trapezoidal (trigate), W/H = 25/8 nm cylindrical, d = 12 nm 1 1

45 75

75 cylindrical, d = 27 nm MOVPE, Au InAs/InGaAs

Si

VG-VI

120

NA

1.90

86

22

407

80

450

year Ron (Ω·μm) DIBL (mV/V)e IONb,d (μA/μm) Q= gm/SS SS (mV/dec)c gm (mS/μm)b,c LG (nm)

EOT (nm)

Review

cross sectional shape/dimensions no. of NWs design substrate growth method material

Table 2. Summary of Selected Reported Performance Metrics of III−V NW-Based MOSFETsa

NA 1

ref

216

Chemical Reviews

K


Chemical Reviews

Review

Figure 6. III−V NW-based MOSFETs. (a−c) Ilustration and SEM image of a completed InAs/InGaAs NW MOSFET on Si together with transfer characteristics of an array with 120 NWs (d = 27 nm, and LG = 75 nm). Sub-100-nm gate-length scaling of vertical InAs/InGaAs nanowire MOSFETs on Si. Reprinted with permission from ref 216. Copyright 2017 IEEE. (d−f) TEM cross section image through the gate of a InAs NW GAA device with d = 15 nm, 3.5−4 nm ZrO2 high-k and W gate metal together with transfer and transconductance characteristics (d = 12 nm and LG = 266 nm). Reprinted with permission from ref 234. Copyright 2016 IEEE. (g−j) SEM images of a InGaAs NW MOSFET at different processing stages together with transfer characterisitics (LG = 75 nm). Reprinted with permission from ref 227. Copyright 2016 IEEE.

reported values, we will here just analyze and compare the topbest device for InAs-based NW MOSFETs produced by each of the described three methods, i.e., vertically grown and integrated (VG-VI), vertically grown but horizontally integrated (VG-HI), and horizontally grown and integrated (HGHI). Table 2 summarizes the performance indicators of these three devices, showing in all cases impressive data such as ION current higher than 300 μA/μm with Q factors (gm/SS) higher than 20. In particular, Kilpi et al.216 reports on a VG-VI device made of InAs NW with a wider gap drain made of InGaAs (see Figure 6a−c). In this way, band to band tunneling is suppressed and a low IOFF (below 1 nA/μm) while maintaining high ION is attained. They also demonstrate a process based on hydrogen silsesquioxane (HSQ) material256 to vary the gate length of the NWs across the same sample and the possibility to integrate up to 120 NWs in the same device. However, comparison with respect to planar/lateral devices indicates that ION suffers from high contact resistance in vertical devices.257 On the other hand, Vasen et al.234 benefits from a hybrid fabrication scheme (VG-HI), where growth, high-k, and metal gate formation occurs in a vertical flow while the rest of the device fabrication occurs in a horizontal flow, yielding an impressive result of a NW with just 12 nm in diameter (see Figure 6d−f). Finally, based on a HG-HI scheme, Zota et al.227 reported the highest ION for any Si- or III−V-based MOSFETs (see Figure 6g−i). Key aspects in this case were gate oxide scaling, improvement of the surface passivation, and optimization of device dimensions. This constitutes one clear

impressive NW MOSFET performance. First, the NW diameter needs to be small to improve electrostatic control and suppress short channel effects.248 Several studies with diameters lower than 30 nm have been published,217,218,222,234 and the diameter effect has been studied in depth in the literature.235,236 There, it is shown how the ION/IOFF ratio and threshold voltage increases when the NW diameter decreases, explained by a bandgap increase due to quantum confinement effects. However, for such reduced diameter dimensions, crystal phase and orientation of the InAs NWs impact the electrical properties of the NW-FETs239 and yield new challenges to measure249 and decrease contact resistance.235,250 On the other hand, the NW sidewall facet, roughness, and the corresponding interface trap density between the oxide and the channel degrades the subthreshold performance.211 Reports on high-k dielectrics/gate engineering in In(Ga)As NWs include Y2O3/HfO2,237 ultrathin parylene films,251 sputtered221 and ALD-deposited252 Al2O3, surface decoration of metal-oxide nanoparticles,253 and partial-gate.254 It is worth mentioning at this point that record performing NW MOSFET and TFET uses digital etching to thin down the NWs with no apparent damage to the wire sidewall.216,255 The majority of the reported devices employ MOVPE to grow the NW structures, either vertically (VLS, SA, TASE) or horizontally (TASE, VLS-SLE). Vertically grown NWs are subsequently integrated (i.e., processed) either in a vertical configuration or deposited on a substrate and horizontally integrated. Instead of benchmarking the performance of all the L


Chemical Reviews

NA 1.91 NA 2 1.75 1.4 1.4 1.4 1.4 NA 200 150 150 NA NA 200−300 260 250−300 185 NA 30 30 30 NA 30 × 38/35 × 25d 20 20/22 20/25 10/18 100/85 SA SA SA Au SA Au Au Au Au Au MOVPE, MOVPE, MOVPE, MOVPE, MOVPE, MOVPE, MOVPE, MOVPE, MOVPE, MOVPE, S S S BG BG BG S S S S Si/InAs Si/In0.7Ga0.3As Si/InGaAs GaSb/InAs(Sb)c InAs/GaSbc InAs/GaSb InAs/GaAsSb/GaSb InAs/In0.1Ga0.9As0.88Sb0.12/ GaSb InAs/InGaAsSb/GaSb InP/GaAsc

a All TFETs are single vertical NW devices. ION and IOFF values should be carefully compared as their definition and normalization procedures differ between publications. Tabulated ION and SS values correspond to best reported values in each work and not necessarily belong to the same NW device. Diameter refers to final value employed in the TFET, which may be thinner that the obtained value after NW growth. Materials combination follows material growth direction. bAbbreviations: HTRJ = heterojunction, S = staggered, BG = broken gap, MOVPE = metalorganic vapor phase epitaxy, SA = selective area, NA = not available, Au = gold catalyzed, EOT = equivalent oxide thickness ION = on current, IOFF = off current, Vds = drain to source voltage, SS = subthreshold swing, min = minimum, av = average, ref = reference. cLateral geometry. dRectangular cross-section. eION/IOFF = 1× 107.

269 270 271 272 273 274 255 275 276 277 2013 2013 2014 2013 2016 2016 2016 2017 2018 2012

2012

1 0.1 1 0.25 0.1 0.05 0.5 0.3 0.1−0.5 0.1 0.05 0.75 NA 25 21 40 NA 320 1400 NA NA NA NA 150 21 21 12 23 30 NA NA 68 48 43 35 50 1 0.1 1 0.5 0.1 0.5 0.5 0.3 0.3 0.3 0.05 0.75 1 × 10 NA 1× 1010 cm Hz1/2 W1−) are reported, irrespective of the material employed. Indeed, the

318 319 320 321 322 323 54 56 324

Review


Chemical Reviews

Review

Figure 8. III−V single and ensemble NW photodetectors. (a) Device configuration and photocurrent response of an intersubband NW heterostructure array PD with response in the LWIR range. Reproduced with permission from ref 324. Copyright 2018 American Chemical Society. (b,c) SEM image of an InAsSb ensemble NW PD with metal partial coating exciting surface plasmon resonances and yielding high resposivity up to 3 μm. Reproduced with permission from ref 320. Copyright 2016 American Chemical Society. (d,e) Device configuration of a ferroelectricenhanced side-gated InP single NW PD together with the I−V characteristics with positive, negative, and without polarization. Reproduced from ref 303. Copyright 2016 American Chemical Society. (f) SEM image of a InP/InAsP single NW SAM APD together with its electrical characteristics. Reproduced with permission from ref 329. Copyright 2017 American Chemical Society.

quantum discs in InP NWs (shown in Figure 8a),56,324 partial coating of InAsSb NWs with Au to excite localized surface plasmon resonances (shown in Figure 8b,c)320,326 or by using ternary materials such as InAsSb,321 GaAsSb,301,314,315 InGaAs,302,308 or InAsP.317 At the single NW level, a photogating layer (see below) has also enhanced the response in the SWIR region.303,305,307 On the other hand, although efficient absorption of light at mid and long wavelength regions is diameter dependent and would require NWs with diameters of hundreds of nanometers,327 some studies reported NW PDs operating in MWIR and LWIR range by means of pattering NWs in clusters328 or intersubband transitions within embedded InAsP quantum discs in InP NWs,324 respectively. Special attention has recently been given to the photogating effect, which is considered as a way of conductance modulation through a photoinduced gate voltage originating from surface trapped charges.330 As seen in many reports,303,305,306 photogating significantly improves the gain of NW PDs but reduces the response speed.330 Of particular interest is the example shown in Figure 8d,e, where Zheng et al.303 showed a ferroelectric polymer side-gated single InP NW PD with a high photoconductive gain of 4.2 × 105, responsivity of 2.8 × 105 A/W, and high detectivity of 9.1 × 1015 Jones. In addition,

responsivity values are often similar or even higher than those reported for thin film PDs,301−303 which is explained by the long carrier lifetime and short transit time due to the good material quality, high carrier mobility, and NW dimensions.287 However, still responsivity and gain values for ensembles are lower than single NW devices, which is due to (1) the complexity of the integration process and (2) the low bandgap materials employed in the ensemble PDs which yield lower responsivity, as explained below. Importantly, almost all the reported values in Tables 5 and 6 are at room temperature. This constitutes a significant advancement in the field of IR PDs, because commercially available PDs based on HgCdTe and InSb typically operate at a costly low temperature.294 Besides, we would like to highlight three main topics that have attracted researcheŕs attention in the past five years namely, detection range extension, photogating effect, and development of innovative avalanche photodetectors. With respect to the detection range of operation, we notice here that there is a tendency to optimize the short wavelength infrared region (SWIR) response (and not only visible region), especially at the ensemble level. Indeed, remarkable SWIR response has been recently achieved by strained InAs NW on Si,319 InAs NW on InP with p−n heterojunctions,318 InAsP Q


Chemical Reviews

Review

demands.347,348 III−V NW-based solar cells are a very interesting approach to enable highly efficient, low cost devices349−353 for many different applications such as tandem configuration on Si solar cells for highly efficient devices,354 the Internet of things355 or space missions.356 First, III−V materials, with their direct, tunable energy bandgap and good minority carrier properties are excellent candidates for PV applications. In particular for a single junction solar cell, GaAs and InP show an energy bandgap very close to the ideal value for power conversion efficiency (PCE) maximization.357,358 In addition to this, III−V materials also enable tandem solar cell configurations, where different materials with specific bandgaps are combined to maximize PCE, with planar PCE records above 46% under concentration.359 On the other hand, the NW geometry offers many advantages for PV devices in particular for vertically oriented array architectures (i.e., NW vertical ensemble or forest). From an optical standpoint, NWs are capable to (1) absorb light from an area larger than their physical cross sections yielding high Isc values while using less material,349,360,361 (2) reduce light emission yielding potentially higher Voc values than planar counterparts,362,363 and (3) tailor the bandgap for high PCE as dissimilar materials can be grown in NWs as they are capable to accommodate strain by the free surface.207 While absorption benefit has been proven experimentally many times,67,364,365 we believe that other aspects for charge carrier separation and collection (e.g., junction geometry and design, surface passivation or electrical contacts) still need to be optimized, as recently reviewed by Otnes and Borgström.366 NW solar cells also offer a potential for low cost. Given their enhanced absorption properties, less material than bulk is consumed (NW surface coverage is only around 13% in current top-class devices57,67). Besides, it is possible to transfer NW arrays into polymer films354,367−369 to ultimately reuse the substrate for subsequent regrowth354,369 or even use substratefree Aerotaxy technique to grow p−n junctions69 (as seen in section 2.2.4). In this section, we will review the actual status of NW solar cell technology by looking at recent device results of vertical NW ensembles, as it is probably the most promising configuration due to the aforementioned absorption resonances, together with the possibility to create heterojunctions and to combine NWs with Si solar cell technology. However, understanding and optimization of NW solar cell technology have been developed from initial studies at single NW level, which will be also mentioned here for some specific cases. For more in-depth III−V NW solar cell understanding and historical development, the reader is referred to several reviews published in the field.349,350,360,363,366,370−374 The actual status of NW solar cell technology has been summarized in Table 7, which adapts and actualizes the reported performance metrics of ensemble III−V NW solar cells from Otnes and Borgström.366 Table 7 includes only publications in the period 2014−2108 and puts special emphasis on growth of material, growth methods, and junction and array design. As it can be observed in Table 7, the majority of the reported devices employ MOVPE as the growth method, nanoimprint lithography (NIL) for array formation and the interest is mainly focused on Ga(In)As57,70,124,136,139,375,376 or InP67,68,148,365,377,378 materials. Particularly impressive in this field is its rapid development over the last 10 years. PCE values have been increased from a

negative photoconductivity (i.e., conductivity decrease with light exposure) in n-InAs307,305,306,331−333 has also been an active topic of debate and can also be explained by photogating as discussed in literature.330,334 However, diameter tuning,335 surface cleaning, and/or passivation seems to revert the negative photoconductivity.304,331,334,335 Finally, NW avalanche photodetectors (APD) were proposed in 2006 for large photocurrent gain and sensitivity to single photon level.336,337 Recently, more sophisticated APD designs with a separate absorption and multiplication region (SAM-APD) in NWs have been reported.329,338,339 Indeed, Farrell et al.338 used a plasmonic optical antenna in InGaAs NWs, whereas Jain et al.329 reported a InP/InAsP NW heterostructure SAM-APD (see Figure 8f) with spectrally tuned absorption at 1.55 μm (i.e., in the InAsP region). 2.3.2.2. III−V Nanowire LEDs. Since the demonstration of the first, axially defined, GaAs NW LED reported in 19923 and the momentum generated after the realization of a GaAs/ GaInP core/shell NW LED on Si in 2008,340 several research groups have been trying to develop highly efficient, compact and bright light NW-based sources. For more in-depth III−V LED understanding and historical development, the reader is referred to other reviews published in the field.174,293 Recent reports (period 2014−2018) on III−V NW LEDs mainly cover sophisticated core/shell structures. For instance, Kawaguchi et al.341 reported on a InP/InAsP/InP NW heterostructure with electroluminescence (EL) in the 1.5-μm wavelength region at room temperature, whereas Berg et al.62 reported on a radial p−i−n junction NW quantum well structure in the AlGaInP material system with GaInP as the active layer, with emission in the red wavelength range after a careful dimension design to optimize light extraction. In a later work, the same group presented a detailed loss efficiency analysis together with some guidelines to make larger improvements in the LED performance.342 Quite recently, crystal phase engineering of NW growth119,343 enabled wurtzite phosphide materials that has been employed to develop AlInP NWs with strong, room temperature emission in the green gap.115 With respect to axial current injection schemes, Scofield et al.130 reported on a n-GaAs/i-InGaAs/pGaAs axial heterostructure with GaAsP diffusion barriers to provide enhanced carrier confinement, providing a 5-fold increase in output intensity. LEDs developed in the NW geometry enable the desired III−V material integration on a Si platform. Recent, outstanding examples of direct growth of III−V LEDs on Si include an InGaAs/InP core/shell multiquantum well with emission at 1500 nm and current conduction through the silicon344 or (In,Ga)As/GaAs coaxial multishell NWsi with RT EL at 985 nm.104 Besides, several works address and envision how to use III−V NWs monolithically integrated with silicon.127,345,346 In particular, Malheiros-Siveira et al.345 showed how stimulated and spontaneous emission of InP NWs can be directly coupled to Si waveguides. On the other hand, Kim et al.127 demonstrated the SA growth of InGaAs NWs on 3D structured and planar silicon-on-insulator (SOI) substrates, together with emission from a SOI grating, which is coupled with an optically pumped single NW through a waveguide. 2.3.3. III−V Nanowire Photovoltaics. Photovoltaics (PV) is a sustainable, low cost, and scalable technology for solar energy conversion into electricity, which will play a significant role to meet the ever-growing world electricity R


Chemical Reviews

Review

Table 7. Summary of Recently Reported Performance Metrics of III−V NW-Based Solar Cellsa,b Jsc (mA/cm2)

Voc (V)

FF (%)

PCE (%)

year

ref

18.2

0.39

46.5

3.3

2016

70

21.08

0.565

63.65

7.58

2014

139

21.3

0.906

79.2

15.3c

2015

57

axial p−n

AlGaAs, in situ thin AlGaAs

6.8

0.860

59

3.5

2018

354

0.01

radial p−i−n

SiOx

15.7

0.5

67.7

5.3

2015

378

NIL

0.25

axial p−i−n

SiOx

13.7

0.66

70.0

6.3

2016

148

p-InP

EBL

0.04

none

22.5

0.55

75.0

9.23

2018

377

p-InP

NIL

1.00

axial p−p−−n axial p−i−n

SiOx

24.6

0.779

72.4

13.8

2013

67

p-InP

NIL

1.00

SiOxd

26.64

0.730

77.0

15.0c

2018

68

p-InPe multilayer graphene p-GaAs

NIL none

0.09 5.1

axial p−p−−n axial p−n radial p−n

29.3 17.16

0.765 0.26

79.4 55.32

17.8c 2.51

2016 2014

365 376

EBL

0.81

axial p−i−n

SiOx GaAs, in situ AlInP, in situ

18.2

0.544

72.1

7.14

2015

136

MBE, Ga

Si p-n junction

EBL

0.01

radial p−i−n

AlInP

7.65

1.16

39.6

3.51

2017

375

MOVPE, SA

Si p-n junction

deep UV

1.00

axial n−i−p

BCB

20.64

0.956

57.8

11.4

2015

124

growth method

substrate

pattern

array area (mm2)

junction geometry

GaAs

MBE, Ga

p-Si

EBL

0.01

radial p−i−n

GaAs

MOVPE, SA MOVPE, Au MOVPE, Au MOVPE, Au MOVPE, Au MOVPE, SA MOVPE, Au MOVPE, Au etch down MOVPE, vdW MOVPE, SA

n-GaAs

EBL

1.00

axial n−i−p

p-GaAs

NIL (SCIL) NIL

1.084

axial p−n

25

p-InP

NIL

p-InP

material

GaAs GaAs InP InP InP InP InP InP InGaAs InGaAs Tandem GaAsP on Si GaAs on Si

peel-off

passivation AlInP, in situ BCB

a

Solar cells were measured under 1 sun illumination. All cases were grown by bottom-up approaches on (111) oriented substrates unless otherwise specified. Under junction geometry, doping order is according to growth direction. bAbbreviations: MOVPE = metalorganic vapor phase epitaxy, SA = selective area, vdW = van der Waals epitaxy, NA = not available, Ga = gallium catalyzed, Au = gold catalyzed, UV = ultraviolet, EBL = electron beam lithography, NIL = nanoimprint lithography, SCIL = substrate conformal imprint lithography, PCE = power conversion efficiency, FF = fill factor, Jsc = short circuit current density, Voc = open circuit voltage, cIndependently confirmed PCE value by a calibration laboratory. dAl containing precursor (TMA) is employed during the SiOx deposition. eInP (100).

few percentages to above 15% at one sun, which reflects the research efforts employed to optimize sunlight absorption, carrier collection efficiency, and all the technological steps necessary in order to integrate millions of NWs into solar cell devices with actual active area values in the mm2 range. In particular, current record PCE values are highlighted in bold in Table 7. In 2015, Sol Voltaics AB presented a GaAs-based NW solar cell with PCE of 15.3% and showed the benefits of using an AlGaAs in situ passivation layer which significantly decreased the dark saturation current density and ideality factor.57 In 2018, Otnes et al. reported a very similar PCE (15.0%) but based on InP material, after having optimized collection efficiency and recombination characteristics of the NWs with the help of EBIC and dark I−V of single NWs, respectively.68 In this notable group of solar cells, we also include the work from van Dam et al.,365 with a PCE value of 17.8%. Although this solar cell has been made by a top-down approach, which limits the benefits of the approach, it constitutes the word record in NW solar cell technology. Finally, it is worth mentioning that in the three commented record cases the device area is 1 mm2, which implies having a parallel connection of millions of NWs. In addition, we have identified in literature (1) InP NW surface passivation, (2) junction geometry and design, (3) front contact optimization, (4) advanced NW solar cell characterization techniques, and (5) tandem designs, as the main hot topics that have attracted attention in the last five years. Next we will address each of these topics. We have also

identified an impressive amount of papers dealing with optical and electrical simulations of NW solar cell arrays,362−364,379−395 but this topic is beyond the scope of this section. By just looking at the number of reports published per material, the InP material has received most attention in the last five years, probably related to its low surface recombination velocity,396−398 which avoids the need of in situ passivation. However, dielectric layers, typically employed during NW solar cell processing for stability and isolation purposes, may degrade the intrinsic InP surface properties.399−401 Accordingly, there is a renewed interest in surface cleaning and passivation of InP NW.29,68,118,146 A new passivation scheme based on Al2O3 with a POx interlayer has been reported to significantly improve PL internal quantum efficiency and lifetime as well as improve the thermal stability of InP surfaces.146 In addition, SiNx has been reported to passivate the InP surface.118 However, a decrease of Voc was as well observed,118 probably due to some surface fixed charge density.402 In this line, a permanent local gate of molybdenum oxide has been reported to increase hole concentration in ptype InP and thus increase charge carrier selectively of the hole contact.403 On the other hand, for arsenide materials the most efficient passivation scheme seems to be in situ growth of high bandgap materials.57,70,132,136,375 With respect to junction design, several authors have recently studied the implications of using Zn in an axial p− i−n configuration. First, the p-doped segment should be long S


Chemical Reviews

Review

Figure 9. Characterization of single NW photovoltaic properties in an ensemble NW solar cell. (a−c) SEM, topographic, and conducting AFM images of GaAs NW array solar cell, enabling identification of photoconductivity issues at single NW level. Reprinted with permission from 409. Copyright 2017 Elsevier. (d,e) Cross section SEM image of a NW solar cell with a tungsten nanoprobe contacting one single NW, together with the obtained EBIC and dark IV curve measurements. Correlation of single NW measurements to performance of fully processed NW array solar cells enabled identification of the performance limiting parameters related to growth and/or processing. Reproduced with permission from ref 68. Copyright 2018 American Chemical Society.

photocurrent (see Figure 9d,e).57,68 Interestingly, the number of publications based on EBIC on III−V single NW devices has been significantly increasing over the past five years.69,118,180,329,405,410−413 Finally, one of the hot topics in NW-based solar cells is the development of a tandem structure, either within a NW414 or by a combination of a NW solar cell with a Si solar cell.415 A tandem structure within the NW with dissimilar materials has not yet been achieved, and most of the research effort has been focused on fabricating NW tandem on Si solar cell. One of the major drawbacks of the latter is the incompatibility of Au seed, typically used for NW growth, with Si solar cell technology. Alternatives to achieve such tandem structure include SA and TASE for direct growth on Si (see section 2.1.3), growth in conventional III−V host substrate with subsequent peel-off and membrane integration or Aerotaxy grown NWs with subsequent membrane integration. Table 7 includes the only two reports on NW/Si tandem solar cell reported so far, clearly indicating a benefit in terms of Voc.124,375 Yao et al. reported a seminal GaAs/Si tandem solar cell with a 11.4% PCE value despite the nonoptimized Si solar cell and an unpassivated GaAs NW top subcell, with suboptimal bandgap value for tandem on Si (see Figure 10a,b).124 Two years later, Wood et al.375 reported a NW/Si tandem solar cell with an optimal bandgap material (GaAs0.75P0.25), also showing Voc addition, but with limited success in terms of PCE values (3.51%) due to current mismatch effects. On the other hand, Sol Voltaics AB has shown initial promising results on a 5 × 5 mm2 peeled NW GaAs cell with a 3.5% PCE value.354 Despite the high Voc obtained (0.860 V), Isc is lower than expected due to a too thin passivation layer (needed for successful peeling) and the remaining Au seed particle, which blocks absorption.354 The FF also suffers from a nonoptimized rear contact on the p-type side of the NWs.354 Another approach has been as well proposed for efficient use of the Sun spectrum with a theoretical conversion efficiency of 48.3% for a triple-junction device, based on a multiterminal configuration of NW solar cells with different materials using lateral spectrum splitting.416 In any case, the development of an efficient tandem structure, irrespective of the final architecture, implies the development of high bandgap material solar cells, which implies careful control of composition and doping along the

enough in order to decouple the substrate from the active NW junction.404 In fact, several groups tend now to intentionally use a small amount of Zn during the otherwise intrinsic segment,68,377 so the junction position is at the top of the NW optimizing photocurrent generation.68 We note here that this approach is very sensitive to the particular growth methods and conditions employed and, in some cases, Zn may be present already in the unintentionally doped intrinsic segment.57,118,148 An alternative approach to reduce Zn diffusion is to invert the growth direction (i.e., n−i−p), which is reported to give higher PCE values in single InP NW solar cells.405 With regard to junction geometry, Otnes and Borgström366 pointed out that, so far, axial junction geometries show higher Voc values than radial and they elaborate on the reasons behind. In any case, substrate patterning has turned out to be a key requirement to ensure controlled and homogeneous growth of NW arrays with optimum NW diameter and pitch to enhance light absorption. Indium−tin oxide (ITO) is the preferred option for the front contact of NW solar cells. Continued efforts to enhance ITO electrical characteristics include the use of a Sn doping contact layer136 and a thin Ti132,136 or In70,406 layer before ITO deposition on Ga(In)As NWs. Interestingly, the ITO can be shaped into a dome on top of the NWs to increase broadband and omnidirectional absorption due to Mie scattering.365 A similar effect was previously reported and linked to a light concentration effect.407 From the characterization point of view, we are getting the first reports on angular dependence of photocurrent in NW solar cells.365,408 In particular, Ghahfarokhi et al. observed 95% of the efficiency (at normal incidence) at an incidence angle of 60° and even an increase in power output at an angle of 15°.408 We would also like to highlight special efforts trying to characterize single vertical NW photovoltaic properties in an ensemble solar cell (made of parallel connection of millions of NW p−n junctions) to better interpret and optimize full ensemble device characteristics. Recent studies include conductive atomic force microscopy (see Figure 9a−c),409 electron beam induced current (EBIC),68,136,377 and single NW dark I−V curves enabled by a nanoprobe inside a SEM.68 Indeed, EBIC characterization of single NW solar cells in an ensemble is of particular importance as it has been proven to be a key tool to guide growth of NW solar cells to optimize T


Chemical Reviews

Review

Figure 10. Progress toward III−V NW-based solar cell tandem structures. (a) Device configuration of a GaAs NW-on-Si tandem cell together with the corresponding I−V characteristics (b), showing voltage addition between both subcells. Reproduced with permission from ref 124. Copyright 2015 American Chemical Society. (c) SEM image of a InP/GaInP Esaki diode together with the I−V curves (d) showing the NDR region.180 Reprinted by permission from ref 46. Copyright 2017 Springer Nature.

Figure 11. Photoluminescence spectra of Mg-doped GaN grown by MOCVD on bulk GaN substrates. In (a) is shown the 3.27 eV DAP spectrum involving the substitutional 0.23 eV MgGa acceptor and residual shallow donors.430 In (b) is shown the so-called blue PL spectrum in highly doped GaNMg, the origin of this spectrum is not definitely established. The spectra are shown for different excitation densities. Reprinted with permission from ref 430. Copyright 2014 AIP Publishing.

NW as seen in section 2.1). Some recent examples of single high bandgap NW solar cells can be found in the literature.78,417−419 In both of the aforementioned tandem configurations, special attention must be given to the development of the

Esaki diode, which is used as the electrical connection between the two subcells. Recently, an Esaki diode between materials with interest for tandem within a NW (GaInP/InP) has been demonstrated (see Figure 10c,d),180 but in the same article, the authors illustrate the difficulties associated with the doping U


Chemical Reviews

Review

surface, and an electron density up to mid 1020 cm−3 can then be obtained for growth on sapphire.426 A similar electron density has recently been demonstrated for Ge-doped GaN (on sapphire).426 Such doping related electron concentrations will be needed in devices with a high power consumption, such as diode lasers and some power devices, to avoid excess Ohmic losses in near-contact regions of the device. Another related recent result is the revision of the so-called Mott limit (defined as the limiting electron concentration for metallic conduction in GaN, i.e., the existence of a Fermi level in the conduction band for free electrons in donor-doped GaN427). Traditionally, this limit has been stated as (1−2) × 1018 cm−3 for GaN,428 but recent data show that this value should be revised upward to about 1 × 1019 cm−3.425,427,429 To ensure metallic conduction, the shallow donor doping concentration should then be well above this limit. Bipolar devices like LEDs also include regions of pconduction, which need to be separately optimized. Mainly due to the lack of very shallow acceptors suitable for p-doping in GaN, the hole density obtained in p-doping is more limited than for the case of n-doping. The only practical dopant for pdoping in GaN is Mg on Ga site, giving a moderately deep acceptor of 0.23 eV,430,431 shallower in InGaN though. MBE growth has the advantage for p-doping that the Mg acceptors are active after introduction into the material, and Mg concentrations up to high 1019 cm−3 can be obtained in MBE GaN by the metal modulated epitaxy growth method.432 The rather low growth rate in MBE (from a few nm per hour up to a fraction of a micrometer per hour, depending on the choice of N source) limits the industrial application of this process, however. The preferred growth process for industrial production of devices is MOVPE, offering a considerably higher growth rate (of the order 1−2 μm per hour). Here the growth temperature for GaN is rather high (1000−1100 °C), leading to incorporation of H in the material. H atoms form complexes with the Mg acceptors, passivating these. An annealing step for acceptor activation removing the H atoms is therefore needed after the main growth process.433 For InGaN layers, common in LED structures, MOCVD growth temperatures are lower, typically around 800 °C. In Figure 11 are shown two PL spectra, related to Mg doped GaN.430 In (a) is shown the PL spectrum related to the MgGa acceptor, i.e., a donor−acceptor (DA) pair emission involving shallow donors and the Mg acceptor, together with LO phonon replicas.430 This is the optical fingerprint of the Mg acceptor in GaN. The broad so-called “blue” emission, also related to Mg but otherwise of unknown origin, is shown in (b). The PL spectra are normalized to the peak value. The hole concentration obtained in p-GaN grown by MOCVD is generally limited to about 2 × 1018 cm−3 at RT, partly due to a low thermal activation of the rather deep Mg acceptor. Another limiting factor in the common growth of GaN on sapphire, is a segregation process occurring at the threading dislocations whereby Mg atoms are incorporated in a different phase not active in p-conduction.434,435 It appears that inclusions of Mg in a different phase (like inversion domains where the Mg atoms are primarily not active as dopants) are abundant around the grown-in threading dislocations, thus drastically lowering the acceptor activation. This problem could obviously be avoided if low defect bulk GaN substrates are employed instead of sapphire (or silicon) substrates in the growth process. The high commercial cost of

value and profile of cathode and anode by trying different dopants and growth directions (p−n or n−p). Core−shell radial Esaki tunnel diodes have been reported as well.181,420

3. III-NITRIDE NANOWIRE MATERIALS AND DEVICES The materials of III-nitride NWs can either be seen as one of all the III−V NWs or can be treated as a unique materials case. A reason for the latter approach is also motivated by the differences in crystal structures of the regular III−Vs and the III−nitrides, with the nitride materials being of hexagonal wurtzite structure with strong polarization effects not so important for the regular III−Vs. Furthermore, the nitride materials stand out in the absence of a suitable substrate material, hence leading to the omnipresence of high dislocation densities in all epitaxially grown GaN materials unless bulk high-quality GaN is used as substrate for growth. This issue of lattice mismatch and huge strain effects with associated straininduced polarization field are indeed a major motivation for the efforts of developing III-nitride devices in the NW form because the narrow diameter and the small footprint of NWs enable nucleation and growth of III-nitride NWs under conditions yielding dislocation-free NW device materials. In the following we first (section 3.1) describe in some depth the material properties of III-nitrides because these are quite special and different from the regular III−V materials family. After this, we present a review (section 3.2) of growth and specific applications of III-nitride NWs. 3.1. III-Nitride Material Properties from Growth of Bulk and Planar Structures

The III-nitride family is composed of AlN, GaN, InN, and related alloys (AlGaN, InGaN, AlInN, etc.). These materials all have direct bandgaps, covering together the energy region 0.7− 6 eV. This situation is obviously favorable for applications in optical devices, such as LEDs and PVs, but these materials are also of great interest for power electronic devices. The materials have in common a great mechanical strength and hardness but also the possibility of a controlled variation of the electrical conductivity within wide limits. The thermal conductivity is also very good. The material properties depend strongly on conditions like purity (including doping), density of structural defects, and strain conditions, and they generally vary strongly with temperature. Ferreyra et al.421 gave a detailed exposition of the properties of the III-nitrides, relevant for electronic applications.421 These properties formed a prerequisite for the strong development effort in III-nitride based planar light-emitting devices witnessed during the last decades.422 The Nobel Prize in Physics in 2014 was awarded to three professors of Japanese origin: I. Akasaki, H. Amano, and S. Nakamura “for the invention of efficient blue LEDs, which has enabled bright and energy saving white light sources” (see the Web site www.nobelprize.org). Electron conduction in GaN has traditionally been realized with Si doping, employing the shallow Si donor (binding energy about 30 meV). This has been an appropriate solution for LED applications, where an electron density of about 1018 cm−3 is sufficient. It turned out that the Si doping for GaN on sapphire was unable to produce electron densities above (1−2) × 1019 cm−3.423 The reason was recently found to be the development of structural defects (inversion domains containing Si) during growth, connected with threading dislocations in the GaN material grown on foreign substrates.424,425 This problem can be solved by a small addition of Al to the growing V


Chemical Reviews

Review

structures but has so far not been demonstrated. Another physical concept has been demonstrated for Mg doping in GaN, namely the hybridization of N-related 2p states in the GaN valence band with Mg dopant levels in the AlGaN layers in the SL stack.443 Because Mg is a deep acceptor in AlN (binding energy of the order 0.5 eV), p-doping may be a bottleneck in the planar LED technology. The superlattice doping concept might in the future work for both n-type and p-type dopings of the AlN sections, possibly avoiding the otherwise serious consequences of deep level donors and acceptors for doping in AlN. The situation for NW-based AlN LEDs looks very good, however, as discussed separately below. AlGaN-based LEDs for applications in the UVC region have been developed for some time, aiming at a variety of applications like water purification, sterilization, disinfection of surfaces, UV curing, printing processes, and more. These LEDs are now marketed with external quantum efficiency (EQE) less than 10%. The main reason behind this rather low value is the low output coupling of the light through the pGaN contact layer. Other problems are a low hole concentration in the p-region due to the deep Mg acceptor level. Because dislocations are serious nonradiative centers in AlGaN, efforts on producing low dislocation density AlN templates on sapphire were essential in the initial stage of development. Recent work using a high reflectance p-metal contact with a transparent AlGaN p-layer has increased the demonstrated external quantum efficiency (EQE) at about 270 nm emission wavelength to 20%.441 Application of modern outcoupling technologies using photonic lattice concepts predicts a light extraction efficiency (LEE) up to 70% in the future.441 The light is then extracted from the backside of the LED structure. InN as a semiconductor is less developed than the wider bandgap nitrides GaN and AlN, and bulk InN material still does not exist. Much more work has been devoted to InGaN, as mentioned above. InN has the lowest energy for the position of the conduction band minimum among the nitride materials445,446 and is therefore vulnerable to defects that affect the electronic properties. Planar InN grown on foreign substrates is highly defective and thus typically n-type because most defects have a tendency to create shallow donors with a few meV binding energy, and the Mott limit for electrons in InN is just about 2 × 1017 cm−3.445,446 Acceptors can also be introduced, and the case of MgIn has been well studied.447 This acceptor has a binding energy of about 60 meV, i.e., a shallow acceptor suitable for p-doping. In practice for planar growth on sapphire, there is only p-type conduction realized in a doping window 3 × 1018 to 3 × 1019 cm−3, at lower doping the material becomes degenerate n-type due to a dominance of shallow donors.447 At Mg-doping above 1020 cm−3, InN becomes n-type due to an abundance of structural defects (such as stacking faults) creating donors.448 Because of such defect-related problems in the present InN planar technology with growth on sapphire, InN devices are not well developed. There is indeed a need for development of high quality bulk InN materials for high quality substrates. This would boost the development of planar InN devices.

bulk GaN wafers prohibits their industrial use at present, however. The status of AlN (AlGaN) as a material for planar device structures is much less developed than the GaN- (InGaN) counterparts. An important property of AlN is that donors are not very shallow. The OAl donor is predicted to be a deep level,436 i.e., unsuitable for doping purposes. A similar situation occurs for the GeGa donor.436 The SiAl donor has a binding energy of about 250 meV, still too deep for efficient electron doping.437,438 In AlxGa1−xN, a similar situation occurs for x ≥ 0.85, while for lower x values the normal substitutional donor state with a binding energy about 60 meV is the lowest energy configuration.439 In fact, at the higher x-values (x > 0.85) and in AlN, the Si donor has DX character, i.e., the Si atom is distorted from its regular position via an axial lattice relaxation. This DX state of the donor holds two electrons, i.e., the donor is negatively charged, while the normal donor (one-electron) state is shallow, of the order 60 meV (See Figure 12).439 Electron conduction in AlxGa1−xN can therefore readily be realized in the composition range x ≤ 0.85. For x > 0.85, the thermal occupation of the DX state becomes gradually smaller for increasing x, and the donor activation (and the conductivity) is then strongly reduced.

Figure 12. Schematic development of the different donor states in AlxGa1−xN:Si, showing the negative two-electron DX state as well as the one-electron donor state and its estimated effective mass energies.438 The horizontal axis represents the bandgap energy, showing that in AlN the DX donor state dominates, making the binding energy of the order 0.25 eV. Reprinted with permission from ref 438. Copyright 2014 AIP Publishing.

A large effort is presently spent on developing UV LEDs440,441 and lasers442 in the planar technology. LEDs may be produced in AlN, typically employing a superlattice concept for the active region to achieve the desired pconductivity.443 In fact, the built-in polarization field itself in a graded Al-composition AlGaN/GaN planar heterojunction induces field ionization of holes to the valence band. This graded structure producing holes by field ionization of both the bulk material and the Mg dopants can be combined with a p−n junction, allowing injection of both 2D and 3D holes into the lower bandgap GaN material.444 This effect is further enhanced by Mg-doping of the AlGaN, adding free holes produced by field ionization of the acceptors.444 A related approach is to use superlattices with alternating GaN-AlGaN thin layers (of the order 10 nm). Such structures have a sawtooth like band profile, promoting field ionization of carriers. Because the Si donors have the lowest binding energy among the donors in AlN, this process might be suitable for n-conduction in AlN

3.2. Synthesis of GaN Nanowires and Related Device Applications

Electronic as well as photonic devices can be very sensitive to the high dislocation densities typically encountered for planar growth of III-nitrides on non-native substrates, such as W


Chemical Reviews

Review

Figure 13. (A) Images from an ETEM video of a GaN NW growing in 3 × 10−2 Torr of NH3 + TMGa at 800 °C. Multiple steps are observed at the catalyst−NW interface. These steps are indicated by the white arrows. (B) At 0.0 s, another GaN NW (⟨11̅00⟩-oriented) growing in 5 × 10−4 Torr of NH3 + TMGa at 800 °C. The projected step height is measured (indicated by the two red arrows) at roughly 0.6 nm. (C) At 1.1 s, the newly nucleated step continues to grow across the catalyst−NW interface. Its position is indicated by the red arrow. (D) At 2.0 s, as the initial step (indicated by the red arrow) approaches the other end of the NW, a second step nucleates on top of the newly formed GaN layer, indicated by the blue arrow. (E) The step originally formed at 0.0 s grows to the edge of the NW as the step nucleated earlier at 2.0 s continues to expand across the catalyst−NW growth interface. The arrows shown in B−E illustrate the approximate locations of the GaN double bilayer growth plane. Reproduced with permission from ref 457. Copyright 2016 American Chemical Society.

orientation of ⟨101̅0⟩ when Au particles are applied.451,452 By changing the Ni content in Ni−Au alloy particles, the GaN NW orientation can be tuned from ⟨101̅0⟩ to ⟨112̅0⟩.451 ⟨101̅0⟩-oriented GaN NWs seeded by Ni particles were also reported.453 However, usage of c-sapphire and c-GaN/sapphire did not lead to vertical ⟨0001⟩-oriented GaN NW growth with Ni particles, indicating a weak effect from the substrate on the NW growth direction.453,454 With Au particles, ⟨0001⟩oriented GaN NWs can be obtained by using Si (111) and MgO (111) substrates.452,455,456 Gamalski et al. reported a direct observation of the GaN NW growth seeded by Au particles with environmental transmission electron microscopy.457 The growth was nonepitaxial and completely determined by the Au particles deposited on a SiN heater chip. The GaN NWs took either ⟨112̅0⟩ or ⟨101̅0⟩ orientation, but the growth front between the Au particle and the GaN NW was always (101̅0). The growth takes place with a double (101̅0) bilayer nucleation at one edge and then flowing across the particle-GaN interface as shown in Figure 13. ⟨112̅0⟩ and ⟨101̅0⟩-oriented GaN NWs are both triangularly shaped, enclosed by (11̅01), (1̅101), and (0001̅) side facets for the former and (21̅1̅2), (2̅112), and (0001̅) side facets for the latter.449,450,452,453 No matter that the GaN NWs grow along ⟨101̅0⟩ or ⟨112̅0⟩ orientation, there is always a (0001̅) side facet. The (0001̅) plane is terminated by N, which could be passivated by H through a formation of N−H bonds.458 This

sapphire, SiC, or Si. Here the large lattice mismatch gives rise to an unwanted strain-induced polarization effect that affects the device performance. However, thanks to the small diameter and footprint of III-nitride NWs, these typically have no, or very few, dislocations and also much reduced polarization fields, which makes GaN NWs important building blocks for nitride optoelectronic devices. Recent studies show that GaN NWs are also of great interest in power transistors with a wrap gate around the NWs. The method to synthesize III−V and Si NWs with metal nanoparticles, known as VLS growth as discussed in section 2.1.1, was also applied for growing GaN NWs at early times. Apart from this, self-organized growth and selective area growth of GaN NWs have been widely studied. In this section, we will focus on the GaN NW growth (bottomup paradigm) with these three methods, based on the growth techniques of MOVPE, MBE, and hydride vapor phase epitaxy (HVPE). At the end, the top-down fabrication of GaN NWs will be discussed because it has been drawing more attention recently. 3.2.1. Growth Seeded by Metal Nanoparticles. Au and Ni particles are commonly used to seed the GaN NW growth. To a large extent, GaN NW orientation is determined by the interface properties between particles and GaN. Apart from this, substrates and growth conditions also affect the growth orientation of the GaN NWs. Ni particles tend to seed the GaN NW growth along ⟨112̅0⟩ direction on r-sapphire and LiAlO2 (100) substrates,449−451 in contrast to the growth X


Chemical Reviews

Review

works. In this way, high quality GaN NWs were obtained with sub-meV line widths of PL peaks, comparable to those of freestanding GaN layers grown by HVPE.469 Self-regulated radius of GaN NWs was reported, which usually leads to an inversely tapered shape at the NW bottom part.468 Even though the GaN NWs are grown under N-rich conditions, the Ga/N ratio at the growth front could be high at the initial growth stage, arising from the different diffusion lengths of Ga and N adatoms along the side facets. This high Ga/N ratio leads to the radial growth and then increases the NW radius. The increased NW radius reduces the Ga diffusion to the NW top, leading to a drop of the Ga/N ratio. Once this Ga/N ratio reduces to a critical value, the NW radial growth ceases and only the axial growth remains. 3.2.2.2. GaN Nanowires by MBE: Doping. Si and Mg dopants are mainly used to obtain n-type and p-type GaN. In general, higher Si and Mg doping can be obtained in GaN NWs compared to the doping in planar GaN films.484,485 However, both Si and Mg contents show spatial inhomogeneity in the GaN NWs, that is, higher concentrations were observed at the periphery of the GaN NWs than in the core (Figure 14). This inhomogeneous distribution of Si and Mg dopants could be related to the growth mechanism, where Si and Mg adatoms reach the growth front at the NW top through diffusion on the side facets of the NWs. Ge doping in the GaN NWs was also studied because the doping concentration could be higher and doping-caused strain may be smaller, compared to the Si doping.486 With the Ge doping, screening of the quantum-confined Stark effect in AlN/GaN NW superlattices was reported.487 3.2.2.3. GaN Nanowires by MBE: Device Structures and LEDs. The geometric nature of the NWs offers control of the movement of carriers to axial, one-dimensional transport and gives opportunities for design and implementation of confinement of carriers and photons in devices. This has formed the basis for polariton lasers, as pioneered by Bhattacharia et al. at the University of Michigan.488 In another publication, this group has demonstrated the monolithic incorporation of a single GaN NW laser with photonic crystal microcavity on silicon (Figure 15).489 InGaN/GaN dot/disk-in-a-wire has been widely used for visible LEDs based on GaN NWs grown by MBE. Strain and indium concentration in this configuration were studied. Besides the biaxial strain arising from the lattice mismatch between InGaN and GaN, hydrostatic strain also exists due to the small radial size of NWs, indicating the different strain relaxations from the NW surface to the core.490,491 This hydrostatic strain can be competitive with the biaxial strain for the indium composition up to 10%. Varied strains in InGaN dots/disks result in different In compositions and then a broad line width of the emissions. LED structures were realized on such GaN NWs with InGaN/GaN dot/disk-in-a-wire active layers and p-GaN grown axially.463,465,466,470,478,492−494 By tuning the In composition in the active layers, electrically excited emissions can be realized in the visible light spectrum. The LED performance was strongly enhanced due to control on the surface recombination by an AlGaN shell. With this, an output power of 1.5 mW was obtained at 70 A/cm2.494 Zhao et al. realized EL emission at a wavelength of 710 nm and the light output power was 6.14 mW at an injection current density of 400 A/cm2.478

surface reconstruction could prevent the Ga adsorption to the (0001̅) plane, leading to an extremely low growth rate. This is why the (0001̅) plane, instead of the (0001) plane, is kinetically formed as one side facet of ⟨101̅0⟩ and ⟨112̅0⟩oriented GaN NWs.459 This low growth rate is also true for shell growth of InGaN/ GaN multiple quantum wells (MQWs), which means that the thickness of InGaN/GaN MQWs grown on (0001̅) are much smaller than those on the other two side facets.450 Meanwhile, the indium incorporation into these side facets are different due to the different crystalline properties. This could lead to different emission wavelengths, which affects the monochromaticity of the emissions. Qian et al.450 reported that no visible InGaN/GaN MQWs are grown on (0001̅) side facets. Taking a thin p-GaN on this side facets for an LED structure into consideration, this side facet may not contribute to the emissions but offers a channel for electrical current to flow through, leading to energy loss. Ra et al. studied ⟨0001⟩-oriented GaN NW growth on Si (111) with Au particles. Such NWs are hexagonal and enclosed by six equivalent (101̅0) m-plane side facets. Because of the enhanced axial growth with particles, an LED structure in the axial direction can be obtained455 besides the core−shell structured LEDs.456 EL of the core−shell structured LEDs did not show any peak wavelength shift at different current injections, in contrast to a blue-shift for the axial structured LEDs.460 This result clearly showed the absence of piezoelectric polarization fields on the core−shell structured LEDs grown on the m-plane side facets. 3.2.2. Self-Organized Growth. 3.2.2.1. GaN Nanowires by MBE: Growth Mechanism. Because of possible impurity incorporation from the metal seed particles, self-organized growth, without using seed particles (including self-seeded growth), was applied to grow GaN NWs. In this method, GaN NWs are grown directly on a bare substrate by controlling the nucleation and growth conditions. Self-organized GaN NWs have been intensively studied with MBE. Such GaN NWs were grown typically under a N-rich condition, where the lateral growth is efficiently reduced and the hexagonal NW shape satisfies the minimal equilibrium total surface energy.461 With this condition satisfied, GaN NWs could be grown vertically on different substrates, including Si (001),462−464 Si (111),465−470 graphene,471−473 diamond,474 Ti,475,476 and Mo.477−479 The orientation of GaN NWs grown in this way is not dependent on the substrate, which is always c-oriented. However, the polarity could be either Ga-polar or N-polar, which seems not controllable by the substrate preparation, including a Gapreflow or usage of a thin AlN nucleation layer.480 In general, it seems that only if the GaN nuclei are formed on the substrate surface, GaN growth will continue on such nuclei in a coriented NW fashion. Self-organized GaN NW growth by MBE is usually identified as following three stages: the incubation stage, the nucleation of GaN NWs, and the elongation of the GaN NWs.163,469,481 The incubation stage depends mostly on the substrate temperature and the Ga flux.163 High substrate temperature and low Ga flux can hugely increase the incubation time. Surface morphology is another factor affecting the incubation time. Usage of an AlN layer or amorphous AlxOy layer can reduce the incubation time and enhance the nucleation of the GaN NWs.482,483 With a high Ga flux and using an AlN layer, Zettler et al. realized GaN NW growth at 875 °C, which is much higher than the temperature commonly used in other Y


Chemical Reviews

Review

Figure 14. (a) 2D map of Mg/(Mg + Ga) ratio in a GaN NW obtained by atom probe tomography and (b) the concentration profile of Mg calculated perpendicular to the NW axis. High resolution energy dispersive X-ray spectroscopy of Si and Ga maps obtained (c) at 200 kV using a FEI Osiris TEM equipped with super X detectors and (d) at 4 kV using a ZEISS Ultra 55 SEM equipped with FlatQuad annular detector. The Si concentration profile is shown in (e). (a,b) Reproduced with permission from ref 484. Copyright 2018 IOP Publishing. (c−e) Reproduced with permission from ref 485. Copyright 2015 American Chemical Society.

nm.499,500,505−508 For UV LEDs and lasers, an AlGaN shell is also needed to suppress the surface recombination, which is the same as the InGaN/GaN disk-in-a-wire LEDs.509 N-type and p-type conductivities could be obtained in graded AlGaN sections without dopants and UV LEDs working at 318 nm was reported in this way.464 Al(Ga)N/GaN MQWs axially grown on GaN NWs were also used to study the intersubband absorption. The intersubband absorption from 1.4 to 3.4 μm was observed for AlN/GaN MQWs. By using AlGaN/GaN MQWs, the intersubband absorption at 4.5−6.4 μm was realized.510−512 MBE was also used to grow InN NWs in this self-organized way. The as-grown InN NWs show high quality with a large electron mobility in the range of 8000−12000 cm2/V s, approaching the theoretically predicted maximum value.513 The background doping in these InN NWs is low so that the NW surface free of Fermi level pinning was observed for the first time.514 Meanwhile, p-type InN was realized based on such InN NWs with a stable p-type surface and an InN p−i−n LED was achieved with a light emission at 0.71 eV.508,515 3.2.2.5. GaN Nanowires by MOVPE. MOVPE was also used to grow GaN NWs in a self-organized method. In contrast to MBE growth where Si substrates were mainly used, c-sapphire was usually used for the self-organized growth of GaN NWs by MOVPE. Self-organized GaN NW growth on graphene was also reported recently.516 Different from the MBE growth where a N-rich condition is necessary, a low V/III ratio of around 20 was used for the GaN NW growth by MOVPE, about 2 orders of magnitude lower than the value used for

Eu-doped GaN was studied to be used as an active layer for planar red LEDs.495 Recently, Sukegawa et al. realized Eudoped GaN NWs by MBE and inserted it into n-type and ptype GaN sections for an LED structure.496 EL emission at 620 nm was observed. Because the Eu doping level is much higher in the GaN NWs than the planar film before luminescence starts to quench, this could be a good option for GaN NWs to realize efficient red LEDs for microLED displays. 3.2.2.4. Al(Ga)N and InN Nanowires by MBE. Apart from the GaN NWs, self-organized Al(Ga)N NWs were also studied with MBE. To obtain Al(Ga)N NWs, a GaN NW stub needs to be grown first. Otherwise, the Al(Ga)N NWs tends to coalesce and form a film due to a low flux of N to enhance the Al migration.497,498 The whole composition range of AlGaN NWs can be obtained in this way.497−500 By using a low growth rate, Mg incorporation into AlN NWs could be enhanced, leading to an achievement of p-type AlN with a hole concentration of 6 × 1017 cm−3 at room temperature.501,502 The surprisingly good dopant activation in this case (considering the Mg acceptor activation energy of the order 0.5 eV), is explained in terms of a higher doping in the near surface region, promoting a formation of a Mg impurity band with a considerably reduced binding energy.501,503 On the basis of this, EL emissions were observed from an AlN p−i−n LED structure with an internal quantum efficiency of about 80% and a turn on voltage of about 6 V (i.e., the AlN bandgap).500,502,504 By tuning the aluminum composition, lasing from AlGaN p−i−n structures can be achieved electrically at room temperature at a wavelength range of 240−340 Z


Chemical Reviews

Review

Figure 15. (a) Schematic representation of NW laser consisting of a single GaN NW and a 2D photonic crystal microcavity. (b) An oblique view SEM image of the fabricated device.489 Reproduced with permission from ref 489. Copyright 2011 AIP Publishing.

planar GaN MOVPE growth.517,518 The other two necessities are a SiN-covered/modified sapphire surface and a high flow of SiH4.517 A flow of SiH4, corresponding to a doping level of 1019 cm−3, can greatly enhance axial growth of GaN NWs. The reason was reported as the SiNx passivation on the side facets of GaN NWs.519,520 Because of the nitridation on the sapphire surface before the growth, GaN NWs grown in this way are Npolar. However, around the N-polar GaN core, Ga-polar GaN is usually observed to grow with an inversion domain boundary in between.521 Ga-polar GaN NWs could be grown if the surface nitridation was not applied, and meanwhile a low growth rate was used. The V/III ratio was as low as 26. The as-grown GaN NWs have m-plane side facets and a pyramidal top. PL measurement at 5 K shows a narrow emission peak from a donor bound exciton recombination (Figure 16), which indicates a good quality of GaN NWs.518 Planar GaN films are usually grown with a much higher V/III ratio as mentioned above to suppress the N-vacancy. However, the PL results in Figure 16 shows that N-vacancy is not an issue for GaN NWs grown at an ultralow V/III ratio. 3.2.2.6. (In)GaN Nanowires by HVPE. Kim et al. reported self-organized GaN NW growth by HVPE.522 The growth temperature was 478 °C, which is much lower than the temperature of >1000 °C for the planar GaN growth by HVPE. This could be a reason why the GaN growth takes place in the NW shape. Similar to self-organized growth by MBE, LED structures with axial InGaN QWs and p-GaN were presented with EL emissions at 466 nm.523 Apart from this, InGaN NWs with a whole composition range could be grown by HVPE as shown by the works from Kuykendall et al. and Zeghouane et al.524,525 3.2.3. Selective-Area Growth. GaN growth shows a selectivity on the surfaces of different materials. For instance, the nucleation of GaN is difficult on SiNx, SiOx, W, and Ti, but it tends to take place on sapphire or GaN. The growth selectivity also depends on the growth conditions/supersaturation. With a patterned layer of SiNx, SiOx, W, or Ti as a mask on a substrate (sapphire or GaN/sapphire), growth takes place selectively from the exposed area of the substrate. Different patterns can be designed depending on requirements. With stripe openings made on the mask, epitaxial lateral overgrowth of GaN can be realized to obtain GaN films with much reduced dislocation density.526 If circular openings in nanometer dimensions are made on the growth mask, GaN NWs can be grown from the openings as shown by Figure 17.

3.2.3.1. GaN Nanowires by MBE. With MBE, Sekiguchi et al. and Kishino et al. reported the selective GaN NW growth on GaN films with a patterned Ti mask.527−530 Growth temperature has to be higher than the typical one for MBE planar GaN growth in order to enhance the growth selectivity together with a low N-flux. The low N-flux was found able to reduce the growth on the side facets, favoring the control on the lateral size of GaN NWs.527 Gotschke et al. studied the growth dependence on the pitch of the opening array.531 According to the wire volume relation to the pitch, the growth was found to be controlled by the adatom diffusion on the growth mask and this diffusion length was about 400 nm at the growth conditions. Polarity affects the GaN NWs growth. It was found that Npolar templates produced fast-growing GaN NWs, while Gapolar templates produced slow-growing pyramidal structures defined by (101̅2) planes.532 Selective area growth of GaN NWs on short AlN/Si stubs was reported, and green LEDs were presented based on such NWs.533 AlGaN NW growth was realized with selective area MBE.499,534 However, a GaN NW stub is also needed for the selective growth of AlGaN NWs, the same as the self-organized growth. AlGaN preferentially grew on the GaN NW stubs, but AlGaN growth on the Ti mask was not avoidable. In this way, AlGaN NWs with band gap emissions from 210 to 327 nm can be grown.534 3.2.3.2. GaN Nanowires by MOVPE: Growth Mechanism. Selective area growth of GaN NWs by MOVPE has been intensively studied. In this case, (101̅1) crystal planes make it a challenge to grow Ga-polar GaN NW by MOVPE due to specific surface properties. (101̅1) planes are of a N-polarity, which is the same as the (0001̅) plane as mentioned in section 3.2.1. Because of the formation of N−H bond, the growth rate of (101̅1) planes could also be extremely low, compared to the growth on (101̅0) m-planes and (0001) plane.459,535,536 According to the growth kinetics, the surfaces with lower growth rates tend to appear in the grown structures and then determine the final structure shape.459 In the case of selective area growth of GaN by MOVPE, the (101̅1) planes usually form during the growth, defining the structure shape as a hexagonal pyramid.526,535 In this sense, growth of GaN NWs defined by six equivalent m-planes does not take place at common growth conditions for planar GaN growth by MOVPE. In 2006, Hersee et al. reported for the first time the Ga-polar GaN NW growth by selective area MOVPE.537 To avoid the growth in the pyramid shape, pulsed growth mode had to be AA


Chemical Reviews

Review

Figure 16. Typical low temperature (5 K) microphotoluminescence measurement of single GaN NWs. The peak full width at halfmaximum of this near band edge emission is 0.95 meV. Donor bound exciton recombinations (D0XA and D0XB) and free A and B excitons (FXA and FXB) are indicated. Intensities are in arbitrary units and in log scale; the inset shows a magnification of the main peak.518 Reprinted with permission from ref 518. Copyright 2011 AIP Publishing. Figure 18. Temporal evolutions of Ga-polar GaN NW growth with the continuous-flow mode. (a) Cross-sectional TEM images of GaN NWs grown for different times. The growth time is presented under each images. All TEM images were recorded along a [112̅0] direction. Scale bar: 50 nm. (b) GaN NW diameter and length dependences on the growth time. The inset shows how the diameter was measured.

axial direction.538,539 Zhang et al. and Tu et al. observed the Ga droplet formation at the NW top after the Ga precursor pulse and the Ga droplet size can be controlled by tuning the supply of the Ga precursor.540,541 In this way, GaN NWs with multiple sections of different cross-sectional sizes were formed and multiple color emissions from single NWs were realized with different InGaN QW growth on different sections.541 We also worked on the Ga-polar GaN NW growth by selective area MOVPE, but we investigated the growth with continuous flows of Ga precursor and NH3 to seek possibilities for the growth to take the vertical NW shape. Our results show that there is a growth condition window to obtain GaN NWs, instead of GaN pyramids.542 In 2012, Choi et al. also reported the Ga-polar GaN NW growth by simultaneously feeding Ga precursor and NH3.543 The V/III ratio should be two orders of magnitude lower than those typically used for planar GaN growth by MOVPE in order to obtain GaN NWs. Figure 18a shows different growth stages of GaN NWs performed by us with the continuous-flow mode. The pyramid facets develop from (101̅3) for the growth in the opening to (101̅2) after GaN grows out of the opening. With continued growth, new facets are formed at the edges between the top pyramid and the vertical side facets, which in the end makes the NW top rough with many tiny crystal planes. Note that after the growth of these samples, growth temperature ramped down fast without a NH3 flow to freeze the growth front. We believe that the rough surface for the 60 and 120 s samples is the true growth front instead of arising from a surface decomposition, because the other three samples show complete crystalline surfaces at the top. Once the NW top gets rough, the lateral growth is inhibited and then the growth continues mainly in the axial direction as shown in Figure 18b.

Figure 17. Selective area growth of GaN NWs. (a) Schematic of a GaN film on a Si (111) substrate with dislocations presented. (b) Template of GaN/Si covered with a SiN mask patterned with nanometer-sized circular openings. (c) GaN NW arrays grown on the patterned template in (b). This SEM image was taken with a 30° tilt of the sample. Scale bar: 10 μm. Inset: A high resolution SEM image of GaN NWs with a scale bar 1 μm.

used at their growth conditions, which means that Ga precursor of trimethylgallium and NH3 flow into the MOVPE chamber sequentially. In this work, the GaN NWs show a similar diameter as the circular openings in the SiN mask and no clear lateral growth on the side facets of m-planes was observed. At the NW top, a truncated pyramid was formed with a top c-plane and (11̅02) inclined planes. No (11̅01) plane was observed in the GaN NWs. Lin et al. and Jung et al. studied the effects of the pulse duration and the interruption time on the GaN NW growth and found both parameters are crucial to limit the lateral growth and enhance the growth in AB


Chemical Reviews

Review

Figure 19. Actual SEM images (left) and kinetic Wulff plots (right) for representative equilibrium shapes: (a) hexagonal pyramid, (b) short NW, and (c) long NW. Full cusps were found in three directions, i.e., [0001], [101̅1], and [101̅0]. Note that a much deeper cusp is observed in the [101̅0] direction for the elongated NW structure. Scale bar: 250 nm.545 Reprinted with permission from ref 545. Copyright 2016 Royal Society of Chemistry.

Figure 20. GaN NW shape and bending of dislocations propagated from GaN template. A dislocation propagated into the GaN NWs, bent into cplane and then was terminated at one m-plane side facet. This caused a faster growth of the corresponding m-plane and an asymmetric shape of the GaN NW (TEM image on the left), in contrast to a symmetric hexagonal shape of GaN NWs free of dislocations (TEM image on the right).

Continuous-flow growth mode under ultralow V/III ratio and pulsed growth mode were found to be facilitating the Gapolar growth in a NW shape instead of a pyramid. This means that the low growth rate of (101̅1) planes can be tackled with both methods. As mentioned above, the surface of (101̅1) planes is usually terminated by hydrogen. However, it was pointed out theoretically that this surface can be covered with a Ga adlayer under Ga-rich conditions instead of bonding with hydrogen, leading to a faster growth rate of it.535,536,544 This agrees with the Ga-polar GaN NW growth with either pulsed mode or continuous-flow mode under a low V/III ratio, where the Ga-rich condition is satisfied. The increased growth rate of (101̅1) planes makes c-plane and (101̅0) m-planes appear during the growth, leading to the NW growth fashion kinetically, as shown in the kinetic Wulff plots in Figure 19.545 As mentioned above, in the GaN NW growth with metal particles, N-polar (0001̅) plane is also terminated by hydrogen, which makes it grow slowly. From this point of view, selective area growth of N-polar GaN could be beneficial for the NW growth fashion, probably with a higher V/III ratio. Growth of N-polar GaN NWs was realized on sapphire or N-polar GaN bulk substrates with continuous flows.520,521,535,546 On sapphire, the N-polarity was obtained with a surface nitridation before the growth starts. The GaN NWs grown in this way are enclosed with six m-planes, and the (0001̅) plane appears at the NW top due to its low growth rate. Carrier gas of a mixture of N2 and H2 was found able to reduce the lateral growth.546

Similar to the self-organized N-polar GaN NWs, Ga-polar domains were always found growing around the N-polar GaN core.521 Wang et al. studied the growth kinetics and mass transport mechanisms for N-polar GaN NWs, including the growth contributions from species impingements on the NW top and on the side facets, as well as the diffusion flux from the mask surface.520 For the growth with a low SiH4 flow (doping level: 1018 cm−3), a critical length of 3.5 μm was found, beyond which the diffusion flux from the mask surface may not contribute to the growth any more. However, such a critical length does not exist or is much larger than the NW length in the work for the growth with a high SiH4 flow (doping level: >1019 cm−3). Up-to-date, selective area MOVPE has been used mainly to grow GaN NWs. It does not seem possible to expand this method to InGaN NW growth because indium does not incorporate into the lattice under so low V/III ratio. However, a higher V/III ratio leads to the InGaN growth in a pyramid fashion, which is the same as for the GaN growth.547 In terms of high Al content AlGaN growth, no selectivity can be realized because Al atoms are much less diffusive on the mask surface, which means that the growth of AlGaN on the mask is not avoidable.548 3.2.3.3. GaN Nanowires by MOVPE: Dislocation Filtering. Dislocations, either from the underlying GaN layer or formed at the interface between the GaN NW and the substrate, may AC


Chemical Reviews

Review

Figure 21. Top view SEM image after the first self-limiting growth step for arrays with pitches: (a) 1 μm, (b) 1.4 μm, and (c) 2 μm. The NW profile after removing the SiO2 filling matrix for arrays with pitches: (d) 1 μm, (e) 1.4 μm, and (f) 2 μm. A 30° tilt view after the second selflimiting growth step for arrays with pitches: (g) 1 μm, (h) 1.4 μm, and (i) 2 μm. Reproduced with permission from ref 570. Copyright 2017 Springer Nature.

3.2.3.4. GaN Nanowires by MOVPE: Optical Properties. Strong yellow luminescence (YL) related to point defects in GaN was observed on the GaN NWs grown with the continuous-flow mode in contrast to the band gap emission.552−555 For the worst case, the band gap emission from the GaN NWs could get completely quenched.520,554 The GaN NWs grown with the pulsed growth mode show weaker YL intensity compared to those grown with the continuousflow mode.553 As mentioned above, decent PL result could be obtained for the self-organized GaN NWs grown directly on sapphire substrates (Figure 16), where a low V/III ratio is similar as the one used here for the selective area growth.518 The low V/III ratio seems not to be a reason for the strong YL and the weak band gap emission from the selectively grown GaN NWs. Instead, a high level doping of Si and/or other impurities may be a possible reason with the growth mask of SiOx or SiNx as the source. Such a Si background doping was reported for selectively grown GaN films with a SiOx/SiNx mask.556 3.2.3.5. GaN Nanowires by MOVPE: Device Structures and LEDs. Recently considerable efforts have been made in development of NW-based LEDs for the visible region.293,557 In theory, the NW LED concept should be excellent, allowing a high volume density of the active region for light emission and also efficient light out-coupling by the regular NW arrays.

propagate through the openings and enter the GaN NWs. Hersee et al. found that dislocations entering the NWs bend into c-plane and then terminate at one m-plane side facet.549 Dislocations which enter the NWs closer to the center propagate upward a longer distance before it bends into the c-plane. Kishino et al. found with MBE growth that for GaN NWs thinner than 200 nm, most of the dislocations bend and terminate to side facets in the 300 nm bottom region of the GaN NWs.528 Such a dislocation filtering accompanies a strong enhancement of donor bound exciton emissions.550 We also found such dislocation behavior during GaN NW growth. However, it was found that the m-plane side facet which terminates the dislocation grows much faster compared to the other side facets free of dislocations, leading to an asymmetric NW growth as shown in Figure 20. This seems true also for the work reported by Choi et al. because the GaN NWs grown from large openings (a high probability for dislocations to propagate through) tend to be irregular in shape.543 To reduce the dislocation propagation into GaN NWs, one way is to use small openings below 100 nm, which can efficiently filter out the dislocations by the mask. Coulon et al. reported another way, that is, a formation of a void under the openings so that the dislocation can terminate at the free surface of the void.551 AD


Chemical Reviews

Review

direct-view microLEDs (MicroLED displays, Yole development report, July 2018). Zhang et al. studied the process on such NW LEDs and found that etching away the QWs at the NW top could benefit a direct light-up of QWs on m-plane side facets with a reduced emission line width.561 Schmidt et al. studied the growth of a 30 nm thick InGaN shell around GaN NWs. InGaN growth at the edges between adjacent m-planes takes place on a locally formed a-plane (112̅0), leading to a much longer wavelength emission (higher indium composition) at the edges compared to the emission from the m-planes (lower indium composition).555 Similar growth behavior was also observed by Griffiths et al.566 Anisotropic growth of AlGaN shell on GaN NW was also reported.567 Al-rich and deficient regions were observed in the AlGaN shell, which was attributed to the longer surface diffusion length of Ga adatoms (compared to Al adatoms) and the different initial strain state of each m-plane side facets of the GaN NWs. Different strain state in InGaN shell on GaN NWs was also reported between different m-plane side facets on the same NW.568 Recently, Nami et al. reported a peak IQE of 62% for the InGaN QWs grown on the GaN NWs and a peak external quantum efficiency of 8.3% was obtained for an unpackaged NW LED emitting at 450 nm.569 The best external quantum efficiency of blue InGaN NW emitters are just about half of the planar counterpart (B. Hahn, private communication 2018). Relevant publications covering the latest developments seem to be missing, but more work is in progress to fulfill the technical promises. The reason behind this lower efficiency has been found to be the creation of defects in the fabrication process, both structural defects and point defects. Structural defects like dislocations and stacking faults have been found in the active region of these structures in spite of the seemingly high regularity of the NW growth pattern. These defects are known as serious sources of nonradiative recombination in any LED structure. In addition, point defects may occur in the NW structures due to the different growth conditions needed (strong YL emissions from GaN NWs as mentioned above) compared to the case of planar structures. These point defect problems (mainly in the active InGaN part) have not yet been widely studied in connection with the NW growth process. Kum et al. reported a method to prepare GaN NWs monolithically with the same diameter and length between differently pitched arrays.570 This work shows totally different growth method and growth mechanism compared with all other works in this section. To achieve this, GaN NWs were obtained through filling deep cavities formed in a 2.9 μm thick SiO2 layer. Figure 21a−c shows the growth after the filling growth, where GaN grows out of the cavities and forms a pyramid top with the same dimension even though the pitch varies from 1 to 2 μm. Such a similar dimension is also clearly shown in Figure 21d−f after the SiO2 was etched away, and the GaN NWs were scratched down. GaN regrowth after removing SiO2 takes place on the side facets, and the final diameter is determined by the bottom size of the top pyramids. With this two-step self-limiting growth, GaN NW arrays with same dimensions can be obtained even though the pitch is different between different arrays (Figure 21g−i). This is different from the normal selective area growth mentioned above, where the GaN NW volume depends on the pitch. With this method, core−shell structured LEDs emitting blue to red light were demonstrated between different NW arrays monolithically, which has potential for applications in microLED displays and

Figure 22. In-plane strain (εxx) evolutions deduced from the PL measurements (a) and the X-ray diffraction experiments (b). The red squares correspond to the NW series on sapphire substrate, while the filled and the open blue circles correspond to two different NW series on silicon substrate. The black lines are the calculated averaged inplane strain (εxx) from 3D strain distribution simulations. Simulated strain maps of 25, 75, 150, and 300 nm high GaN NWs on top of a GaN layer on sapphire substrate (c).577 Reprinted with permission from ref 577. Copyright 2013 AIP Publishing.

InGaN QWs were grown on such GaN NWs. Unlike the MBE growth, InGaN QWs are usually grown on the side facets of GaN NWs, which forms a core−shell structure. A high active layer volume can be achieved by using long GaN NWs. If the GaN NW top is flat, InGaN also grows on it. Side facets of mplanes are nonpolar and atomically smooth in contrast to the striation surface on m-plane films,558 making GaN NWs attractive for nitride LEDs. However, the InGaN QWs grown on the side facets are usually inversely tapered, indicating thicker InGaN layers at the NW top than the bottom. Meanwhile, the indium composition at the NW top is much higher than the one at the bottom, depending on the NW length.554,559−565 Such thicker InGaN QWs at the NW top can resemble a quantum ring structure or even a set of six quantum dots for emissions that occur for low current injection densities. This situation thus may appear favorable for LED applications operated under ultralow current densities, like for AE


Chemical Reviews

Review

Figure 23. (a) Schematic and (b) microphotograph of fabricated vertical GaN NW-based MOSFET with inverted p-GaN channel. The 45°-tilted scanning electron microscope images (c) before and (d) after filling with resist.580 Reprinted with permission from ref 580, Copyright 2018 IEEE.

highlighted in the plenary talk given at the International Workshop on Nitride Semiconductors 2018 in Kanazawa by Prof. Tomas Palacios, vertical gated all-around n+ n n+ NWs seem to solve many of the issues encountered by planar high electron mobility transistor technology such as increase in the breakdown voltage as well as increase of the effective current density.583 This is a natural next step to the previously demonstrated vertical fin-FET technology.584 Similar approaches have also recently been published by the Waag group at the Braunschweig University, both as wrap-around gated n−i−n vertical transistors572 and for normally off GaN NW transistors with an inverted p-channel,580 with device structures shown in Figure 23. This top-down method was also used to obtain axial NW LEDs by etching a planar GaN LED wafer. Such axial NW LEDs do not seem possible to be obtained with the bottom-up GaN NW growth. Because of the strain relaxation, a blue-shift of the emitting wavelength was observed with this axial NW LED structure compared to the original planar LED wafer.574,585−589 By decreasing the NW diameter to 40 nm, a blue-shift of 178 nm was observed when a planar nitride LEDs emitting red light at 650 nm was used.589−591 This means that by controlling the NW size, NW LEDs covering red, green, and blue colors can be realized, which can be a potential candidate for microLED displays. With this method, uniform arrays of AlN and AlGaN NWs were obtained with MOVPE-grown AlN and AlGaN films on sapphire substrates.592−594 An AlGaN single QW grown around the AlN NWs shows emission between 229 and 265 nm.593 Because arrays of AlN NWs cannot be fabricated directly with selective area MOVPE, this method is unique to obtain Al(Ga)N NWs and study the applications of Al(Ga)N NWs on UV LEDs by MOVPE.

phosphor-free solid-state lighting based on blue, green, and red LEDs. 3.2.4. Top-Down Synthesis Method. Besides the bottom-up methods discussed above, the top-down method is getting more attention to make GaN NWs. In this method, the GaN NWs were obtained with a dry etch on planar GaN wafers with an etch mask of nanometer dimensions.571−574 The rough surface after the dry etching could be smoothed with KOH-based wet etching, leading to a formation of GaN NWs enclosed by m-planes or a-planes depending on the etchant concentration.575 The GaN NWs, synthesized in this way, are from the original GaN films grown with MOVPE, where growth conditions optimized for a high quality of GaN can be applied. Compared with the bottom-up GaN NW growth by MOVPE, high V/III ratios and absences of a high flow of a SiH4 and SiOx or SiNx mask ensure a high quality of GaN NWs with low background dopants and point defects. By controlling the etch mask size, GaN NWs as small as 17 nm can be made with smooth side facets.571 With the GaN NWs standing on sapphire substrates, optically pumped lasing was realized in spite of the reduced reflectivity of optical modes at the GaN/sapphire interface compared to the GaN/air interface. Single-mode lasing spectra with an line width 300 plenary/invited talks at international conferences and workshops.

ACKNOWLEDGMENTS This work was performed with financial support from the Swedish Research Council, the Foundation for Strategic Research, the Knut and Alice Wallenberg Foundation, and the Swedish Energy Agency. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement 641023 (Nano-Tandem). This publication reflects only the author’s views, and the funding agency is not responsible for any use that may be made of the information it contains. We thank Dr. Gaute Otnes, Dr. Johannes Svensson, and Mohammad Karimi for their insightful comments and critical reading of parts of this review. REFERENCES (1) Wagner, R. S.; Ellis, W. C. Vapor-Liquid-Solid Mechanism of Single Crystal Growth. Appl. Phys. Lett. 1964, 4, 89−90. (2) Givargizov, E. I. Fundamental Aspects of VLS Growth. In Vapour Growth and Epitaxy; Cullen, G. W., Kaldis, E., Parker, R. L., Rooymans, C. J. M., Eds.; Elsevier, 1975; pp 20−30. (3) Haraguchi, K.; Katsuyama, T.; Hiruma, K.; Ogawa, K. GaAs P-n Junction Formed in Quantum Wire Crystals. Appl. Phys. Lett. 1992, 60, 745−747. (4) Hiruma, K.; Murakoshi, H.; Yazawa, M.; Katsuyama, T. SelfOrganized Growth of GaAsInAs Heterostructure Nanocylinders by Organometallic Vapor Phase Epitaxy. J. Cryst. Growth 1996, 163, 226−231. (5) Duan, X.; Lieber, C. M. General Synthesis of Compound Semiconductor Nanowires. Adv. Mater. 2000, 12, 298−302. (6) Johnson, J. C.; Choi, H.-J.; Knutsen, K. P.; Schaller, R. D.; Yang, P.; Saykally, R. J. Single Gallium Nitride Nanowire Lasers. Nat. Mater. 2002, 1, 106−110. (7) Björk, M. T.; Ohlsson, B. J.; Sass, T.; Persson, A. I.; Thelander, C.; Magnusson, M. H.; Deppert, K.; Wallenberg, L. R.; Samuelson, L. AI


Chemical Reviews

Review

(27) Dick, K. A.; Caroff, P. Metal-Seeded Growth of III−V Semiconductor Nanowires: Towards Gold-Free Synthesis. Nanoscale 2014, 6, 3006−3021. (28) Borgström, M. T.; Wallentin, J.; Trägårdh, J.; Ramvall, P.; Ek, M.; Wallenberg, L. R.; Samuelson, L.; Deppert, K. In Situ Etching for Total Control over Axial and Radial Nanowire Growth. Nano Res. 2010, 3, 264−270. (29) Cui, Y.; Wang, J.; Plissard, S. R.; Cavalli, A.; Vu, T. T. T.; van Veldhoven, R. P. J.; Gao, L.; Trainor, M.; Verheijen, M. A.; Haverkort, J. E. M.; et al. Efficiency Enhancement of InP Nanowire Solar Cells by Surface Cleaning. Nano Lett. 2013, 13, 4113−4117. (30) Perea, D. E.; Hemesath, E. R.; Schwalbach, E. J.; Lensch-Falk, J. L.; Voorhees, P. W.; Lauhon, L. J. Direct Measurement of Dopant Distribution in an Individual Vapour−Liquid−Solid Nanowire. Nat. Nanotechnol. 2009, 4, 315−319. (31) Assali, S.; Zardo, I.; Plissard, S.; Kriegner, D.; Verheijen, M. A.; Bauer, G.; Meijerink, A.; Belabbes, A.; Bechstedt, F.; Haverkort, J. E. M.; et al. Direct Band Gap Wurtzite Gallium Phosphide Nanowires. Nano Lett. 2013, 13, 1559−1563. (32) Berg, A.; Lehmann, S.; Vainorius, N.; Gustafsson, A.; Pistol, M.E.; Wallenberg, L. R.; Samuelson, L.; Borgström, M. T. Growth and Characterization of Wurtzite GaP Nanowires with Control over Axial and Radial Growth by Use of HCl In-Situ Etching. J. Cryst. Growth 2014, 386, 47−51. (33) Poole, P. J.; Dalacu, D.; Wu, X.; Lapointe, J.; Mnaymneh, K. Interplay between Crystal Phase Purity and Radial Growth in InP Nanowires. Nanotechnology 2012, 23, 385205. (34) Ghalamestani, S. G.; Heurlin, M.; Wernersson, L.-E.; Lehmann, S.; Dick, K. A. Growth of InAs/InP Core−Shell Nanowires with Various Pure Crystal Structures. Nanotechnology 2012, 23, 285601. (35) Ameruddin, A. S.; Fonseka, H. A.; Caroff, P.; Wong-Leung, J.; Op het Veld, R. L. M.; Boland, J. L.; Johnston, M. B.; Tan, H. H.; Jagadish, C. InxGa1-XAs Nanowires with Uniform Composition, Pure Wurtzite Crystal Phase and Taper-Free Morphology. Nanotechnology 2015, 26, 205604. (36) Lehmann, S.; Wallentin, J.; Jacobsson, D.; Deppert, K.; Dick, K. A. A General Approach for Sharp Crystal Phase Switching in InAs, GaAs, InP, and GaP Nanowires Using Only Group V Flow. Nano Lett. 2013, 13, 4099−4105. (37) Joyce, H. J.; Gao, Q.; Tan, H. H.; Jagadish, C.; Kim, Y.; Zhang, X.; Guo, Y.; Zou, J. Twin-Free Uniform Epitaxial GaAs Nanowires Grown by a Two-Temperature Process. Nano Lett. 2007, 7, 921−926. (38) Heurlin, M.; Magnusson, M. H.; Lindgren, D.; Ek, M.; Wallenberg, L. R.; Deppert, K.; Samuelson, L. Continuous Gas-Phase Synthesis of Nanowires with Tunable Properties. Nature 2012, 492, 90−94. (39) Fortuna, S. A.; Li, X. Metal-Catalyzed Semiconductor Nanowires: A Review on the Control of Growth Directions. Semicond. Sci. Technol. 2010, 25, 024005. (40) Krishnamachari, U.; Borgstrom, M.; Ohlsson, B. J.; Panev, N.; Samuelson, L.; Seifert, W.; Larsson, M. W.; Wallenberg, L. R. DefectFree InP Nanowires Grown in [001] Direction on InP (001). Appl. Phys. Lett. 2004, 85, 2077−2079. (41) Cavalli, A.; Wang, J.; Esmaeil Zadeh, I.; Reimer, M. E.; Verheijen, M. A.; Soini, M.; Plissard, S. R.; Zwiller, V.; Haverkort, J. E. M.; Bakkers, E. P. A. M. High-Yield Growth and Characterization of ⟨100⟩ InP p−n Diode Nanowires. Nano Lett. 2016, 16, 3071−3077. (42) Fonseka, H. A.; Caroff, P.; Wong-Leung, J.; Ameruddin, A. S.; Tan, H. H.; Jagadish, C. Nanowires Grown on InP (100): Growth Directions, Facets, Crystal Structures, and Relative Yield Control. ACS Nano 2014, 8, 6945−6954. (43) Wang, J.; Plissard, S. R.; Verheijen, M. A.; Feiner, L.-F.; Cavalli, A.; Bakkers, E. P. A. M. Reversible Switching of InP Nanowire Growth Direction by Catalyst Engineering. Nano Lett. 2013, 13, 3802−3806. (44) Yuan, X.; Caroff, P.; Wong-Leung, J.; Fu, L.; Tan, H. H.; Jagadish, C. Tunable Polarity in a III-V Nanowire by Droplet Wetting and Surface Energy Engineering. Adv. Mater. 2015, 27, 6096−6103.

(45) Car, D.; Wang, J.; Verheijen, M. A.; Bakkers, E. P. A. M.; Plissard, S. R. Rationally Designed Single-Crystalline Nanowire Networks. Adv. Mater. 2014, 26, 4875−4879. (46) Gazibegovic, S.; Car, D.; Zhang, H.; Balk, S. C.; Logan, J. A.; de Moor, M. W. A.; Cassidy, M. C.; Schmits, R.; Xu, D.; Wang, G.; et al. Epitaxy of Advanced Nanowire Quantum Devices. Nature 2017, 548, 434−438. (47) de la Mata, M.; Magen, C.; Caroff, P.; Arbiol, J. Atomic Scale Strain Relaxation in Axial Semiconductor III-V Nanowire Heterostructures. Nano Lett. 2014, 14, 6614−6620. (48) Svensson, J.; Dey, A. W.; Jacobsson, D.; Wernersson, L.-E. III− V Nanowire Complementary Metal−Oxide Semiconductor Transistors Monolithically Integrated on Si. Nano Lett. 2015, 15, 7898− 7904. (49) Zannier, V.; Ercolani, D.; Gomes, U. P.; David, J.; Gemmi, M.; Dubrovskii, V. G.; Sorba, L. Catalyst Composition Tuning: The Key for the Growth of Straight Axial Nanowire Heterostructures with Group III Interchange. Nano Lett. 2016, 16, 7183−7190. (50) Ameruddin, A. S.; Caroff, P.; Tan, H. H.; Jagadish, C.; Dubrovskii, V. G. Understanding the Growth and Composition Evolution of Gold-Seeded Ternary InGaAs Nanowires. Nanoscale 2015, 7, 16266−16272. (51) Dagytė, V.; Heurlin, M.; Zeng, X.; Borgström, M. T. Growth Kinetics of Ga x In (1− x) P Nanowires Using Triethylgallium as Ga Precursor. Nanotechnology 2018, 29, 394001. (52) Berg, A.; Lenrick, F.; Vainorius, N.; Beech, J. P.; Wallenberg, L. R.; Borgstrom, M. T. Growth Parameter Design for Homogeneous Material Composition in Ternary GaxIn1-XP Nanowires. Nanotechnology 2015, 26, 435601. (53) Takiguchi, M.; Yokoo, A.; Nozaki, K.; Birowosuto, M. D.; Tateno, K.; Zhang, G.; Kuramochi, E.; Shinya, A.; Notomi, M. Continuous-Wave Operation and 10-Gb/s Direct Modulation of InAsP/InP Sub-Wavelength Nanowire Laser on Silicon Photonic Crystal. Apl Photonics 2017, 2, 046106. (54) Kuyanov, P.; LaPierre, R. R. Photoluminescence and Photocurrent from InP Nanowires with InAsP Quantum Dots Grown on Si by Molecular Beam Epitaxy. Nanotechnology 2015, 26, 315202. (55) Lind, E.; Memišević, E.; Dey, A. W.; Wernersson, L. III-V Heterostructure Nanowire Tunnel FETs. IEEE J. Electron Devices Soc. 2015, 3, 96−102. (56) Karimi, M.; Jain, V.; Heurlin, M.; Nowzari, A.; Hussain, L.; Lindgren, D.; Stehr, J. E.; Buyanova, I. A.; Gustafsson, A.; Samuelson, L.; et al. Room-Temperature InP/InAsP Quantum Discs-in-Nanowire Infrared Photodetectors. Nano Lett. 2017, 17, 3356−3362. (57) Åberg, I.; Vescovi, G.; Asoli, D.; Naseem, U.; Gilboy, J. P.; Sundvall, C.; Dahlgren, A.; Svensson, K. E.; Anttu, N.; Björk, M. T.; et al. A GaAs Nanowire Array Solar Cell With 15.3% Efficiency at 1 Sun. IEEE J. Photovolt 2016, 6, 185−190. (58) Dagytė, V.; Barrigón, E.; Zhang, W.; Zeng, X.; Heurlin, M.; Otnes, G.; Anttu, N.; Borgström, M. T. Time-Resolved Photoluminescence Characterization of GaAs Nanowire Arrays on Native Substrate. Nanotechnology 2017, 28, 505706. (59) Wallentin, J.; Jacobsson, D.; Osterhoff, M.; Borgstrom, M. T.; Salditt, T. Bending and Twisting Lattice Tilt in Strained Core-Shell Nanowires Revealed by Nanofocused X-Ray Diffraction. Nano Lett. 2017, 17, 4143−4150. (60) Shi, T.; Jackson, H. E.; Smith, L. M.; Jiang, N.; Gao, Q.; Tan, H. H.; Jagadish, C.; Zheng, C.; Etheridge, J. Emergence of Localized States in Narrow GaAs/AlGaAs Nanowire Quantum Well Tubes. Nano Lett. 2015, 15, 1876−1882. (61) Heurlin, M.; Stankevic, T.; Mickevicius, S.; Yngman, S.; Lindgren, D.; Mikkelsen, A.; Feidenhans’l, R.; Borgstrom, M. T.; Samuelson, L. Structural Properties of Wurtzite InP-InGaAs Nanowire Core-Shell Heterostructures. Nano Lett. 2015, 15, 2462−2467. (62) Berg, A.; Yazdi, S.; Nowzari, A.; Storm, K.; Jain, V.; Vainorius, N.; Samuelson, L.; Wagner, J. B.; Borgström, M. T. Radial Nanowire Light-Emitting Diodes in the (AlxGa1−x)YIn1−YP Material System. Nano Lett. 2016, 16, 656−662. AJ


Chemical Reviews

Review

(63) Heurlin, M.; Hultin, O.; Storm, K.; Lindgren, D.; Borgstrom, M. T.; Samuelson, L. Synthesis of Doped InP Core-Shell Nanowires Evaluated Using Hall Effect Measurements. Nano Lett. 2014, 14, 749−753. (64) Otnes, G.; Heurlin, M.; Zeng, X.; Borgstrom, M. T. InxGa1-XP Nanowire Growth Dynamics Strongly Affected by Doping Using Diethylzinc. Nano Lett. 2017, 17, 702−707. (65) Lindelow, F.; Heurlin, M.; Otnes, G.; Dagyte, V.; Lindgren, D.; Hultin, O.; Storm, K.; Samuelson, L.; Borgstrom, M. Doping Evaluation of InP Nanowires for Tandem Junction Solar Cells. Nanotechnology 2016, 27, 065706. (66) Troian, A.; Otnes, G.; Zeng, X.; Chayanun, L.; Dagytė, V.; Hammarberg, S.; Salomon, D.; Timm, R.; Mikkelsen, A.; Borgström, M. T.; et al. Nanobeam X-Ray Fluorescence Dopant Mapping Reveals Dynamics of in Situ Zn-Doping in Nanowires. Nano Lett. 2018, 18, 6461−6468. (67) Wallentin, J.; Anttu, N.; Asoli, D.; Huffman, M.; Åberg, I.; Magnusson, M. H.; Siefer, G.; Fuss-Kailuweit, P.; Dimroth, F.; Witzigmann, B.; et al. InP Nanowire Array Solar Cells Achieving 13.8% Efficiency by Exceeding the Ray Optics Limit. Science 2013, 339, 1057−1060. (68) Otnes, G.; Barrigón, E.; Sundvall, C.; Svensson, K. E.; Heurlin, M.; Siefer, G.; Samuelson, L.; Åberg, I.; Borgströ m, M. T. Understanding InP Nanowire Array Solar Cell Performance by Nanoprobe-Enabled Single Nanowire Measurements. Nano Lett. 2018, 18, 3038−3046. (69) Barrigón, E.; Hultin, O.; Lindgren, D.; Yadegari, F.; Magnusson, M. H.; Samuelson, L.; Johansson, L. I. M.; Björk, M. T. GaAs Nanowire Pn-Junctions Produced by Low-Cost and HighThroughput Aerotaxy. Nano Lett. 2018, 18, 1088−1092. (70) Boulanger, J. P.; Chia, A. C. E.; Wood, B.; Yazdi, S.; Kasama, T.; Aagesen, M.; LaPierre, R. R. Characterization of a Ga-Assisted GaAs Nanowire Array Solar Cell on Si Substrate. IEEE J. Photovolt. 2016, 6, 661−667. (71) Balaghi, L.; Tauchnitz, T.; Huebner, R.; Bischoff, L.; Schneider, H.; Helm, M.; Dimakis, E. Droplet-Confined Alternate Pulsed Epitaxy of GaAs Nanowires on Si Substrates down to CMOS-Compatible Temperatures. Nano Lett. 2016, 16, 4032−4039. (72) Russo-Averchi, E.; Vukajlovic Plestina, J. V.; Tuetuencueoglu, G.; Matteini, F.; Dalmau-Mallorqui, A.; de la Mata, M.; Rueffer, D.; Potts, H. A.; Arbiol, J.; Conesa-Boj, S.; Fontcuberta i Morral, A. High Yield of GaAs Nanowire Arrays on Si Mediated by the Pinning and Contact Angle of Ga. Nano Lett. 2015, 15, 2869−2874. (73) Ermez, S.; Jones, E. J.; Crawford, S. C.; Gradecak, S. SelfSeeded Growth of GaAs Nanowires by Metal-Organic Chemical Vapor Deposition. Cryst. Growth Des. 2015, 15, 2768−2774. (74) Heiss, M.; Russo-Averchi, E.; Dalmau-Mallorqui, A.; Tuetuencueoglu, G.; Matteini, F.; Rueffer, D.; Conesa-Boj, S.; Demichel, O.; Alarcon-Llado, E.; Fontcuberta i Morral, A. III-V Nanowire Arrays: Growth and Light Interaction. Nanotechnology 2014, 25, 014015. (75) Priante, G.; Patriarche, G.; Oehler, F.; Glas, F.; Harmand, J.-C. Abrupt GaP/GaAs Interfaces in Self-Catalyzed Nanowires. Nano Lett. 2015, 15, 6036−6041. (76) Oehler, F.; Cattoni, A.; Scaccabarozzi, A.; Patriarche, G.; Glas, F.; Harmand, J.-C. Measuring and Modeling the Growth Dynamics of Self-Catalyzed GaP Nanowire Arrays. Nano Lett. 2018, 18, 701−708. (77) Zhang, Y.; Sanchez, A. M.; Sun, Y.; Wu, J.; Aagesen, M.; Huo, S.; Kim, D.; Jurczak, P.; Xu, X.; Liu, H. Influence of Droplet Size on the Growth of Self-Catalyzed Ternary GaAsP Nanowires. Nano Lett. 2016, 16, 1237−1243. (78) Zhang, Y.; Wu, J.; Aagesen, M.; Holm, J.; Hatch, S.; Tang, M.; Huo, S.; Liu, H. Self-Catalyzed Ternary Core−Shell GaAsP Nanowire Arrays Grown on Patterned Si Substrates by Molecular Beam Epitaxy. Nano Lett. 2014, 14, 4542−4547. (79) Wu, J.; Li, Y.; Kubota, J.; Domen, K.; Aagesen, M.; Ward, T.; Sanchez, A.; Beanland, R.; Zhang, Y.; Tang, M.; et al. Wafer-Scale Fabrication of Self-Catalyzed 1.7. EV GaAsP Core-Shell Nanowire Photocathode on Silicon Substrates. Nano Lett. 2014, 14, 2013−2018.

(80) Conesa-Boj, S.; Kriegner, D.; Han, X.-L.; Plissard, S.; Wallart, X.; Stangl, J.; Fontcuberta i Morral, A.; Caroff, P. Gold-Free Ternary III-V Antimonide Nanowire Arrays on Silicon: Twin-Free down to the First Bilayer. Nano Lett. 2014, 14, 326−332. (81) Li, L.; Pan, D.; Xue, Y.; Wang, X.; Lin, M.; Su, D.; Zhang, Q.; Yu, X.; So, H.; Wei, D.; et al. Near Full-Composition-Range HighQuality GaAs1-XSbx Nanowires Grown by Molecular-Beam Epitaxy. Nano Lett. 2017, 17, 622−630. (82) Gomes, U. P.; Ercolani, D.; Zannier, V.; David, J.; Gemmi, M.; Beltram, F.; Sorba, L. Nucleation and Growth Mechanism of SelfCatalyzed InAs Nanowires on Silicon. Nanotechnology 2016, 27, 255601. (83) Zhang, G.; Tateno, K.; Birowosuto, M. D.; Notomi, M.; Sogawa, T.; Gotoh, H. Controlled 1.1−1.6 Mu m Luminescence in Gold-Free Multi-Stacked InAs/InP Heterostructure Nanowires. Nanotechnology 2015, 26, 115704. (84) Gao, Q.; Dubrovskii, V. G.; Caroff, P.; Wong-Leung, J.; Li, L.; Guo, Y.; Fu, L.; Tan, H. H.; Jagadish, C. Simultaneous Selective-Area and Vapor-Liquid-Solid Growth of InP Nanowire Arrays. Nano Lett. 2016, 16, 4361−4367. (85) Schuster, F.; Kapraun, J.; Malheiros-Silveira, G. N.; Deshpande, S.; Chang-Hasnain, C. J. Site-Controlled Growth of Monolithic InGaAs/InP Quantum Well Nanopillar Lasers on Silicon. Nano Lett. 2017, 17, 2697−2702. (86) Mattila, M.; Hakkarainen, T.; Jiang, H.; Kauppinen, E. I.; Lipsanen, H. Effect of Substrate Orientation on the Catalyst-Free Growth of InP Nanowires. Nanotechnology 2007, 18, 155301. (87) Fontcuberta i Morral, A.; Colombo, C.; Abstreiter, G.; Arbiol, J.; Morante, J. R. Nucleation Mechanism of Gallium-Assisted Molecular Beam Epitaxy Growth of Gallium Arsenide Nanowires. Appl. Phys. Lett. 2008, 92, 063112. (88) Bastiman, F.; Kuepers, H.; Somaschini, C.; Geelhaar, L. Growth Map for Ga-Assisted Growth of GaAs Nanowires on Si(111) Substrates by Molecular Beam Epitaxy. Nanotechnology 2016, 27, 095601. (89) Matteini, F.; Tutuncuoglu, G.; Mikulik, D.; Vukajlovic-Plestina, J.; Potts, H.; Leran, J.-B.; Carter, W. C.; Fontcuberta i Morral, A. Impact of the Ga Droplet Wetting, Morphology, and Pinholes on the Orientation of GaAs Nanowires. Cryst. Growth Des. 2016, 16, 5781− 5786. (90) Vukajlovic-Plestina, J.; Kim, W.; Ghisalberti, L.; Varnavides, G.; Tütüncuoglu, G.; Potts, H.; Friedl, M.; Güniat, L.; Carter, W. C.; Dubrovskii, V. G.; Fontcuberta i Morral, A. Fundamental Aspects to Localize Self-Catalyzed III-V Nanowires on Silicon. Nat. Commun. 2019, 10, 869. (91) Plissard, S.; Larrieu, G.; Wallart, X.; Caroff, P. High Yield of Self-Catalyzed GaAs Nanowire Arrays Grown on Silicon via Gallium Droplet Positioning. Nanotechnology 2011, 22, 275602. (92) Stettner, T.; Zimmermann, P.; Loitsch, B.; Doeblinger, M.; Regler, A.; Mayer, B.; Winnerl, J.; Matich, S.; Riedl, H.; Kaniber, M.; Abstreiter, G.; Koblmüller, G.; Finley. Coaxial GaAs-AlGaAs CoreMultishell Nanowire Lasers with Epitaxial Gain Control. Appl. Phys. Lett. 2016, 108, 011108. (93) Heiss, M.; Fontana, Y.; Gustafsson, A.; Wüst, G.; Magen, C.; O’Regan, D. D.; Luo, J. W.; Ketterer, B.; Conesa-Boj, S.; Kuhlmann, A. V.; et al. Self-Assembled Quantum Dots in a Nanowire System for Quantum Photonics. Nat. Mater. 2013, 12, 439−444. (94) Jeon, N.; Loitsch, B.; Morkoetter, S.; Abstreiter, G.; Finley, J.; Krenner, H. J.; Koblmueller, G.; Lauhon, L. J. Alloy Fluctuations Act as Quantum Dot-like Emitters in GaAs-AlGaAs Core-Shell Nanowires. ACS Nano 2015, 9, 8335−8343. (95) Wu, J.; Ramsay, A.; Sanchez, A.; Zhang, Y.; Kim, D.; Brossard, F.; Hu, X.; Benamara, M.; Ware, M. E.; Mazur, Y. I.; et al. Defect-Free Self-Catalyzed GaAs/GaAsP Nanowire Quantum Dots Grown on Silicon Substrate. Nano Lett. 2016, 16, 504−511. (96) Priante, G.; Glas, F.; Patriarche, G.; Pantzas, K.; Oehler, F.; Harmand, J.-C. Sharpening the Interfaces of Axial Heterostructures in Self-Catalyzed AIGaAs Nanowires: Experiment and Theory. Nano Lett. 2016, 16, 1917−1924. AK


Chemical Reviews

Review

(97) Scarpellini, D.; Somaschini, C.; Fedorov, A.; Bietti, S.; Frigeri, C.; Grillo, V.; Esposito, L.; Salvalaglio, M.; Marzegalli, A.; Montalenti, F.; et al. InAs/GaAs Sharply Defined Axial Heterostructures in SelfAssisted Nanowires. Nano Lett. 2015, 15, 3677−3683. (98) Chen, H.-L.; Himwas, C.; Scaccabarozzi, A.; Rale, P.; Oehler, F.; Lemaître, A.; Lombez, L.; Guillemoles, J.-F.; Tchernycheva, M.; Harmand, J.-C.; et al. Determination of N-Type Doping Level in Single GaAs Nanowires by Cathodoluminescence. Nano Lett. 2017, 17, 6667−6675. (99) Boland, J. L.; Casadei, A.; Tuetuencueoglu, G.; Matteini, F.; Davies, C. L.; Jabeen, F.; Joyce, H. J.; Herz, L. M.; Fontcuberta i Morral, A.; Johnston, M. B. Increased Photoconductivity Lifetime in GaAs Nanowires by Controlled N-Type and p-Type Doping. ACS Nano 2016, 10, 4219−4227. (100) Goktas, N. I.; Fiordaliso, E. M.; LaPierre, R. R. Doping Assessment in GaAs Nanowires. Nanotechnology 2018, 29, 234001. (101) Dastjerdi, M. H. T.; Fiordaliso, E. M.; Leshchenko, E. D.; Akhtari-Zavareh, A.; Kasama, T.; Aagesen, M.; Dubrovskii, V. G.; LaPierre, R. R. Three-Fold Symmetric Doping Mechanism in GaAs Nanowires. Nano Lett. 2017, 17, 5875−5882. (102) Chia, A. C. E.; LaPierre, R. R. Electrostatic Model of Radial Pn Junction Nanowires. J. Appl. Phys. 2013, 114, 074317. (103) Boland, J. L.; Conesa-Boj, S.; Parkinson, P.; Tütüncüoglu, G.; Matteini, F.; Rüffer, D.; Casadei, A.; Amaduzzi, F.; Jabeen, F.; Davies, C. L.; et al. Modulation Doping of GaAs/AlGaAs Core−Shell Nanowires With Effective Defect Passivation and High Electron Mobility. Nano Lett. 2015, 15, 1336−1342. (104) Dimakis, E.; Jahn, U.; Ramsteiner, M.; Tahraoui, A.; Grandal, J.; Kong, X.; Marquardt, O.; Trampert, A.; Riechert, H.; Geelhaar, L. Coaxial Multishell (In,Ga)As/GaAs Nanowires for Near-Infrared Emission on Si Substrates. Nano Lett. 2014, 14, 2604−2609. (105) Shaw, D. W. Selective Epitaxial Deposition of Gallium Arsenide in Holes. J. Electrochem. Soc. 1966, 113, 904−908. (106) Andrews, D. A.; Rejman-Greene, M. a. Z.; Wakefield, B.; Davies, G. J. Selective Area Growth of InP/InGaAs Multiple Quantum Well Laser Structures by Metalorganic Molecular Beam Epitaxy. Appl. Phys. Lett. 1988, 53, 97−98. (107) Yoo, H.; Hayes, J. R.; Caneau, C.; Bhat, R.; Koza, M. Fabrication of Lateral Planar InP/GaInAsP Heterojunction Bipolar Transistor by Selective Area Epitaxial Growth. Electron. Lett. 1989, 25, 191−192. (108) Hamano, T.; Hirayama, H.; Aoyagi, Y. New Technique for Fabrication of Two-Dimensional Photonic Bandgap Crystals by Selective Epitaxy. Jpn. J. Appl. Phys. 1997, 36, L286. (109) Ikejiri, K.; Sato, T.; Yoshida, H.; Hiruma, K.; Motohisa, J.; Hara, S.; Fukui, T. Growth Characteristics of GaAs Nanowires Obtained by Selective Area Metal−Organic Vapour-Phase Epitaxy. Nanotechnology 2008, 19, 265604. (110) Tomioka, K.; Mohan, P.; Noborisaka, J.; Hara, S.; Motohisa, J.; Fukui, T. Growth of Highly Uniform InAs Nanowire Arrays by Selective-Area MOVPE. J. Cryst. Growth 2007, 298, 644−647. (111) Inari, M.; Takeda, J.; Motohisa, J.; Fukui, T. Selective Area MOVPE Growth of InP and InGaAs Pillar Structures for InP-Based Two-Dimensional Photonic Crystals. Phys. E 2004, 21, 620−624. (112) Motohisa, J.; Noborisaka, J.; Takeda, J.; Inari, M.; Fukui, T. Catalyst-Free Selective-Area MOVPE of Semiconductor Nanowires on (111)B Oriented Substrates. J. Cryst. Growth 2004, 272, 180−185. (113) Berg, A.; Caroff, P.; Shahid, N.; Lockrey, M. N.; Yuan, X.; Borgstrom, M. T.; Tan, H. H.; Jagadish, C. Growth and Optical Properties of In (x) Ga1-x P Nanowires Synthesized by Selective-Area Epitaxy. Nano Res. 2017, 10, 672−682. (114) Bologna, N.; Wirths, S.; Francaviglia, L.; Campanini, M.; Schmid, H.; Theofylaktopoulos, V.; Moselund, K. E.; Fontcuberta i Morral, A.; Erni, R.; Riel, H.; et al. Dopant-Induced Modifications of GaxIn(1−x)P Nanowire-Based p−n Junctions Monolithically Integrated on Si(111). ACS Appl. Mater. Interfaces 2018, 10, 32588− 32596. (115) Gagliano, L.; Kruijsse, M.; Schefold, J. D. D.; Belabbes, A.; Verheijen, M. A.; Meuret, S.; Koelling, S.; Polman, A.; Bechstedt, F.;

Haverkort, J. E. M.; et al. Efficient Green Emission from Wurtzite AlxIn1−XP Nanowires. Nano Lett. 2018, 18, 3543−3549. (116) Farrell, A. C.; Lee, W.-J.; Senanayake, P.; Haddad, M. A.; Prikhodko, S. V.; Huffaker, D. L. High-Quality InAsSb Nanowires Grown by Catalyst-Free Selective-Area Metal−Organic Chemical Vapor Deposition. Nano Lett. 2015, 15, 6614−6619. (117) Ren, D.; Farrell, A. C.; Williams, B. S.; Huffaker, D. L. Seeding Layer Assisted Selective-Area Growth of As-Rich InAsP Nanowires on InP Substrates. Nanoscale 2017, 9, 8220−8228. (118) Zhong, Z.; Li, Z.; Gao, Q.; Li, Z.; Peng, K.; Li, L.; Mokkapati, S.; Vora, K.; Wu, J.; Zhang, G.; et al. Efficiency Enhancement of Axial Junction InP Single Nanowire Solar Cells by Dielectric Coating. Nano Energy 2016, 28, 106−114. (119) Gao, Q.; Saxena, D.; Wang, F.; Fu, L.; Mokkapati, S.; Guo, Y.; Li, L.; Wong-Leung, J.; Caroff, P.; Tan, H. H.; et al. Selective-Area Epitaxy of Pure Wurtzite InP Nanowires: High Quantum Efficiency and Room-Temperature Lasing. Nano Lett. 2014, 14, 5206−5211. (120) Heurlin, M.; Anttu, N.; Camus, C.; Samuelson, L.; Borgstrom, M. T. In Situ Characterization of Nanowire Dimensions and Growth Dynamics by Optical Reflectance. Nano Lett. 2015, 15, 3597−3602. (121) Chu, H.-J.; Yeh, T.-W.; Stewart, L.; Dapkus, P. D. Wurtzite InP Nanowire Arrays Grown by Selective Area MOCVD. Phys. Status Solidi C 2010, 7, 2494−2497. (122) Ikejiri, K.; Noborisaka, J.; Hara, S.; Motohisa, J.; Fukui, T. Mechanism of Catalyst-Free Growth of GaAs Nanowires by Selective Area MOVPE. J. Cryst. Growth 2007, 298, 616−619. (123) Tomioka, K.; Tanaka, T.; Hara, S.; Hiruma, K.; Fukui, T. III− V Nanowires on Si Substrate: Selective-Area Growth and Device Applications. IEEE J. Sel. Top. Quantum Electron. 2011, 17, 1112− 1129. (124) Yao, M.; Cong, S.; Arab, S.; Huang, N.; Povinelli, M. L.; Cronin, S. B.; Dapkus, P. D.; Zhou, C. Tandem Solar Cells Using GaAs Nanowires on Si: Design, Fabrication, and Observation of Voltage Addition. Nano Lett. 2015, 15, 7217−7224. (125) Tomioka, K.; Izhizaka, F.; Fukui, T. Selective-Area Growth of InAs Nanowires on Ge and Vertical Transistor Application. Nano Lett. 2015, 15, 7253−7257. (126) Borg, M.; Schmid, H.; Moselund, K. E.; Signorello, G.; Gignac, L.; Bruley, J.; Breslin, C.; Das Kanungo, P.; Werner, P.; Riel, H. Vertical III−V Nanowire Device Integration on Si(100). Nano Lett. 2014, 14, 1914−1920. (127) Kim, H.; Farrell, A. C.; Senanayake, P.; Lee, W.-J.; Huffaker, D. L. Monolithically Integrated InGaAs Nanowires on 3D Structured Silicon-on-Insulator as a New Platform for Full Optical Links. Nano Lett. 2016, 16, 1833−1839. (128) Shapiro, J. N.; Lin, A.; Wong, P. S.; Scofield, A. C.; Tu, C.; Senanayake, P. N.; Mariani, G.; Liang, B. L.; Huffaker, D. L. InGaAs Heterostructure Formation in Catalyst-Free GaAs Nanopillars by Selective-Area Metal-Organic Vapor Phase Epitaxy. Appl. Phys. Lett. 2010, 97, 243102. (129) Hiruma, K.; Tomioka, K.; Mohan, P.; Yang, L.; Noborisaka, J.; Hua, B.; Hayashida, A.; Fujisawa, S.; Hara, S.; Motohisa, J.; et al. Fabrication of Axial and Radial Heterostructures for Semiconductor Nanowires by Using Selective-Area Metal-Organic Vapor-Phase Epitaxy https://www.hindawi.com/journals/jnt/2012/169284/abs/ (accessed Dec 8, 2018). (130) Scofield, A. C.; Lin, A.; Haddad, M.; Huffaker, D. L. Axial Diffusion Barriers in Near-Infrared Nanopillar LEDs. Nano Lett. 2014, 14, 6037−6041. (131) Kanungo, P. D.; Schmid, H.; Björk, M. T.; Gignac, L. M.; Breslin, C.; Bruley, J.; Bessire, C. D.; Riel, H. Selective Area Growth of III−V Nanowires and Their Heterostructures on Silicon in a Nanotube Template: Towards Monolithic Integration of NanoDevices. Nanotechnology 2013, 24, 225304. (132) Mariani, G.; Scofield, A. C.; Hung, C.-H.; Huffaker, D. L. GaAs Nanopillar-Array Solar Cells Employing in Situ Surface Passivation. Nat. Commun. 2013, 4, 1497. AL


Chemical Reviews

Review

Measurements on the Same Single Nanowire. Nano Lett. 2016, 16, 205−211. (152) Hultin, O.; Otnes, G.; Samuelson, L.; Storm, K. Simplifying Nanowire Hall Effect Characterization by Using a Three-Probe Device Design. Nano Lett. 2017, 17, 1121−1126. (153) Lindgren, D.; Hultin, O.; Heurlin, M.; Storm, K.; Borgström, M. T.; Samuelson, L.; Gustafsson, A. Study of Carrier Concentration in Single InP Nanowires by Luminescence and Hall Measurements. Nanotechnology 2015, 26, 045705. (154) Burgess, T.; Saxena, D.; Mokkapati, S.; Li, Z.; Hall, C. R.; Davis, J. A.; Wang, Y.; Smith, L. M.; Fu, L.; Caroff, P.; Tan, M. H.; Jagadish, C. Doping-Enhanced Radiative Efficiency Enables Lasing in Unpassivated GaAs Nanowires. Nat. Commun. 2016, 7, 11927. (155) Yang, F.; Messing, M. E.; Mergenthaler, K.; Ghasemi, M.; Johansson, J.; Wallenberg, L. R.; Pistol, M.-E.; Deppert, K.; Samuelson, L.; Magnusson, M. H. Zn-Doping of GaAs Nanowires Grown by Aerotaxy. J. Cryst. Growth 2015, 414, 181−186. (156) Schmidt, V.; Mensch, P. F. J.; Karg, S. F.; Gotsmann, B.; Das Kanungo, P.; Schmid, H.; Riel, H. Using the Seebeck Coefficient to Determine Charge Carrier Concentration, Mobility, and Relaxation Time in InAs Nanowires. Appl. Phys. Lett. 2014, 104, 012113. (157) Yazdi, S.; Berg, A.; Borgström, M. T.; Kasama, T.; Beleggia, M.; Samuelson, L.; Wagner, J. B. Doping GaP Core−Shell Nanowire Pn-Junctions: A Study by Off-Axis Electron Holography. Small 2015, 11, 2687−2695. (158) Chia, A. C. E.; Boulanger, J. P.; LaPierre, R. R. Unlocking Doping and Compositional Profiles of Nanowire Ensembles Using SIMS. Nanotechnology 2013, 24, 045701. (159) Du, S.; Burgess, T.; Gault, B.; Gao, Q.; Bao, P.; Li, L.; Cui, X.; Kong Yeoh, W.; Liu, H.; Yao, L.; et al. Quantitative Dopant Distributions in GaAs Nanowires Using Atom Probe Tomography. Ultramicroscopy 2013, 132, 186−192. (160) Cui, Y.; Duan, X.; Hu, J.; Lieber, C. M. Doping and Electrical Transport in Silicon Nanowires. J. Phys. Chem. B 2000, 104, 5213− 5216. (161) Zeng, X.; Mourão, R. T.; Otnes, G.; Hultin, O.; Dagytė, V.; Heurlin, M.; Borgström, M. T. Electrical and Optical Evaluation of n -Type Doping in In x Ga (1− x) P Nanowires. Nanotechnology 2018, 29, 255701. (162) Tchernycheva, M.; Harmand, J. C.; Patriarche, G.; Travers, L.; Cirlin, G. E. Temperature Conditions for GaAs Nanowire Formation by Au-Assisted Molecular Beam Epitaxy. Nanotechnology 2006, 17, 4025. (163) Fernández-Garrido, S.; Zettler, J. K.; Geelhaar, L.; Brandt, O. Monitoring the Formation of Nanowires by Line-of-Sight Quadrupole Mass Spectrometry: A Comprehensive Description of the Temporal Evolution of GaN Nanowire Ensembles. Nano Lett. 2015, 15, 1930− 1937. (164) Killeen, K. P.; Breiland, W. G. In Situ Spectral Reflectance Monitoring of III-V Epitaxy. J. Electron. Mater. 1994, 23, 179−183. (165) Reinhardt, F.; Richter, W.; Müller, A. B.; Gutsche, D.; Kurpas, P.; Ploska, K.; Rose, K. C.; Zorn, M. GaAs Surface Control during Metalorganic Vapor Phase Epitaxy by Reflectance Anisotropy Spectroscopy. J. Vac. Sci. Technol., B: Microelectron. Process. Phenom. 1993, 11, 1427−1430. (166) Namazi, L.; Ghalamestani, S. G.; Lehmann, S.; Zamani, R. R.; Dick, K. A. Direct Nucleation, Morphology and Compositional Tuning of InAs 1− x Sb x Nanowires on InAs (111) B Substrates. Nanotechnology 2017, 28, 165601. (167) Deppert, K.; Bovin, J.-O.; Malm, J.-O.; Samuelson, L. A New Method to Fabricate Size-Selected Compound Semiconductor Nanocrystals: Aerotaxy. J. Cryst. Growth 1996, 169, 13−19. (168) Metaferia, W.; Sivakumar, S.; Persson, A. R.; Geijselaers, I.; Wallenberg, L. R.; Deppert, K.; Samuelson, L.; Magnusson, M. H. NType Doping and Morphology of GaAs Nanowires in Aerotaxy. Nanotechnology 2018, 29, 285601. (169) Metaferia, W.; Persson, A. R.; Mergenthaler, K.; Yang, F.; Zhang, W.; Yartsev, A.; Wallenberg, R.; Pistol, M.-E.; Deppert, K.;

(133) Ishizaka, F.; Hiraya, Y.; Tomioka, K.; Fukui, T. Growth of Wurtzite GaP in InP/GaP Core-Shell Nanowires by Selective-Area MOVPE. J. Cryst. Growth 2015, 411, 71−75. (134) Mohan, P.; Motohisa, J.; Fukui, T. Realization of Conductive InAs Nanotubes Based on Lattice-Mismatched InP/InAs Core-Shell Nanowires. Appl. Phys. Lett. 2006, 88, 013110. (135) Tomioka, K.; Yoshimura, M.; Fukui, T. A III−V Nanowire Channel on Silicon for High-Performance Vertical Transistors. Nature 2012, 488, 189−192. (136) Nakai, E.; Chen, M.; Yoshimura, M.; Tomioka, K.; Fukui, T. InGaAs Axial-Junction Nanowire-Array Solar Cells. Jpn. J. Appl. Phys. 2015, 54, 015201. (137) Wang, F.; Gao, Q.; Peng, K.; Li, Z.; Li, Z.; Guo, Y.; Fu, L.; Smith, L. M.; Tan, H. H.; Jagadish, C. Spatially Resolved Doping Concentration and Nonradiative Lifetime Profiles in Single Si-Doped InP Nanowires Using Photoluminescence Mapping. Nano Lett. 2015, 15, 3017−3023. (138) Arab, S.; Yao, M.; Zhou, C.; Dapkus, P. D.; Cronin, S. B. Doping Concentration Dependence of the Photoluminescence Spectra of N-Type GaAs Nanowires. Appl. Phys. Lett. 2016, 108, 182106. (139) Yao, M.; Huang, N.; Cong, S.; Chi, C.-Y.; Seyedi, M. A.; Lin, Y.-T.; Cao, Y.; Povinelli, M. L.; Dapkus, P. D.; Zhou, C. GaAs Nanowire Array Solar Cells with Axial p−i−n Junctions. Nano Lett. 2014, 14, 3293−3303. (140) Tomioka, K.; Motohisa, J.; Fukui, T. III-V Nanowire Channel on Si: From High-Performance Vertical FET to Steep-Slope Devices. In 2015 International Symposium on VLSI Technology, Systems and Applications; 2015; pp 1−2. (141) Mårtensson, T.; Borgström, M.; Seifert, W.; Ohlsson, B. J.; Samuelson, L. Fabrication of Individually Seeded Nanowire Arrays by Vapour−Liquid−Solid Growth. Nanotechnology 2003, 14, 1255. (142) Mårtensson, T.; Carlberg, P.; Borgström, M.; Montelius, L.; Seifert, W.; Samuelson, L. Nanowire Arrays Defined by Nanoimprint Lithography. Nano Lett. 2004, 4, 699−702. (143) Pierret, A.; Hocevar, M.; Diedenhofen, S. L.; Algra, R. E.; Vlieg, E.; Timmering, E. C.; Verschuuren, M. A.; Immink, G. W. G.; Verheijen, M. A.; Bakkers, E. P. A. M. Generic Nano-Imprint Process for Fabrication of Nanowire Arrays. Nanotechnology 2010, 21, 065305. (144) Munshi, A. M.; Dheeraj, D. L.; Fauske, V. T.; Kim, D. C.; Huh, J.; Reinertsen, J. F.; Ahtapodov, L.; Lee, K. D.; Heidari, B.; van Helvoort, A. T. J.; et al. Position-Controlled Uniform GaAs Nanowires on Silicon Using Nanoimprint Lithography. Nano Lett. 2014, 14, 960−966. (145) Haas, F.; Sladek, K.; Winden, A.; von der Ahe, M.; Weirich, T. E.; Rieger, T.; Lüth, H.; Grützmacher, D.; SchäPers, T.; Hardtdegen, H. Nanoimprint and Selective-Area MOVPE for Growth of GaAs/ InAs Core/Shell Nanowires. Nanotechnology 2013, 24, 085603. (146) Black, L. E.; Cavalli, A.; Verheijen, M. A.; Haverkort, J. E. M.; Bakkers, E. P. A. M.; Kessels, W. M. M. Effective Surface Passivation of InP Nanowires by Atomic-Layer-Deposited Al2O3 with POx Interlayer. Nano Lett. 2017, 17, 6287−6294. (147) Otnes, G.; Heurlin, M.; Graczyk, M.; Wallentin, J.; Jacobsson, D.; Berg, A.; Maximov, I.; Borgstrom, M. T. Strategies to Obtain Pattern Fidelity in Nanowire Growth from Large-Area Surfaces Patterned Using Nanoimprint Lithography. Nano Res. 2016, 9, 2852− 2861. (148) Cavalli, A.; Cui, Y.; Kölling, S.; Verheijen, M. A.; Plissard, S. R.; Wang, J.; Koenraad, P. M.; Haverkort, J. E. M.; Bakkers, E. P. A. M. Influence of Growth Conditions on the Performance of InP Nanowire Solar Cells. Nanotechnology 2016, 27, 454003. (149) Wallentin, J.; Borgström, M. T. Doping of Semiconductor Nanowires. J. Mater. Res. 2011, 26, 2142−2156. (150) Storm, K.; Halvardsson, F.; Heurlin, M.; Lindgren, D.; Gustafsson, A.; Wu, P. M.; Monemar, B.; Samuelson, L. Spatially Resolved Hall Effect Measurement in a Single Semiconductor Nanowire. Nat. Nanotechnol. 2012, 7, 718−722. (151) Hultin, O.; Otnes, G.; Borgström, M. T.; Bjö rk, M.; Samuelson, L.; Storm, K. Comparing Hall Effect and Field Effect AM


Chemical Reviews

Review

Samuelson, L.; et al. GaAsP Nanowires Grown by Aerotaxy. Nano Lett. 2016, 16, 5701−5707. (170) Yan, R.; Gargas, D.; Yang, P. Nanowire Photonics. Nat. Photonics 2009, 3, 569−576. (171) Dasgupta, N. P.; Sun, J.; Liu, C.; Brittman, S.; Andrews, S. C.; Lim, J.; Gao, H.; Yan, R.; Yang, P. 25th Anniversary Article: Semiconductor Nanowires − Synthesis, Characterization, and Applications. Adv. Mater. 2014, 26, 2137−2184. (172) Royo, M.; De Luca, M.; Rurali, R.; Zardo, I. A Review on III− V Core−Multishell Nanowires: Growth, Properties, and Applications. J. Phys. Appl. Phys. 2017, 50, 143001. (173) Ning, C.-Z.; Dou, L.; Yang, P. Bandgap Engineering in Semiconductor Alloy Nanomaterials with Widely Tunable Compositions. Nat. Rev. Mater. 2017, 2, 17070. (174) Zhang, Y.; Wu, J.; Aagesen, M.; Liu, H. III−V Nanowires and Nanowire Optoelectronic Devices. J. Phys. D: Appl. Phys. 2015, 48, 463001. (175) Fang, M.; Han, N.; Wang, F.; Yang, Z.; Yip, S.; Dong, G.; Hou, J. J.; Chueh, Y.; Ho, J. C. III−V Nanowires: Synthesis, Property Manipulations, and Device Applications. J. Nanomater. 2014, 2014, 1−14. (176) Wallentin, J.; Osterhoff, M.; Wilke, R. N.; Persson, K.-M.; Wernersson, L.-E.; Sprung, M.; Salditt, T. Hard X-Ray Detection Using a Single 100 Nm Diameter Nanowire. Nano Lett. 2014, 14, 7071−7076. (177) Vitiello, M. S.; Viti, L.; Coquillat, D.; Knap, W.; Ercolani, D.; Sorba, L. One Dimensional Semiconductor Nanostructures: An Effective Active-Material for Terahertz Detection. APL Mater. 2015, 3, 026104. (178) Baig, S. A.; Boland, J. L.; Damry, D. A.; Tan, H. H.; Jagadish, C.; Joyce, H. J.; Johnston, M. B. An Ultrafast Switchable Terahertz Polarization Modulator Based on III−V Semiconductor Nanowires. Nano Lett. 2017, 17, 2603−2610. (179) Nadar, S.; Rolland, C.; Lampin, J.-F.; Wallart, X.; Caroff, P.; Leturcq, R. Tunnel Junctions in a III−V Nanowire by Surface Engineering. Nano Res. 2015, 8, 980−989. (180) Zeng, X.; Otnes, G.; Heurlin, M.; Mourão, R. T.; Borgström, M. T. InP/GaInP Nanowire Tunnel Diodes. Nano Res. 2018, 11, 2523−2531. (181) Tizno, O.; Ganjipour, B.; Heurlin, M.; Thelander, C.; Borgström, M. T.; Samuelson, L. Radial Tunnel Diodes Based on InP/InGaAs Core-Shell Nanowires. Appl. Phys. Lett. 2017, 110, 113501. (182) Rocci, M.; Rossella, F.; Gomes, U. P.; Zannier, V.; Rossi, F.; Ercolani, D.; Sorba, L.; Beltram, F.; Roddaro, S. Tunable Esaki Effect in Catalyst-Free InAs/GaSb Core−Shell Nanowires. Nano Lett. 2016, 16, 7950−7955. (183) Standing, A.; Assali, S.; Gao, L.; Verheijen, M. A.; van Dam, D.; Cui, Y.; Notten, P. H. L.; Haverkort, J. E. M.; Bakkers, E. P. A. M. Efficient Water Reduction with Gallium Phosphide Nanowires. Nat. Commun. 2015, 6, 7824. (184) Kornienko, N.; Gibson, N. A.; Zhang, H.; Eaton, S. W.; Yu, Y.; Aloni, S.; Leone, S. R.; Yang, P. Growth and Photoelectrochemical Energy Conversion of Wurtzite Indium Phosphide Nanowire Arrays. ACS Nano 2016, 10, 5525−5535. (185) Stettner, T.; Kostenbader, T.; Ruhstorfer, D.; Bissinger, J.; Riedl, H.; Kaniber, M.; Koblmüller, G.; Finley, J. J. Direct Coupling of Coherent Emission from Site-Selectively Grown III−V Nanowire Lasers into Proximal Silicon Waveguides. ACS Photonics 2017, 4, 2537−2543. (186) Kim, H.; Lee, W.-J.; Farrell, A. C.; Morales, J. S. D.; Senanayake, P.; Prikhodko, S. V.; Ochalski, T. J.; Huffaker, D. L. Monolithic InGaAs Nanowire Array Lasers on Silicon-on-Insulator Operating at Room Temperature. Nano Lett. 2017, 17, 3465−3470. (187) Lee, W.-J.; Kim, H.; Farrell, A. C.; Senanayake, P.; Huffaker, D. L. Nanopillar Array Band-Edge Laser Cavities on Silicon-onInsulator for Monolithic Integrated Light Sources. Appl. Phys. Lett. 2016, 108, 081108.

(188) Wang, Z.; Tian, B.; Pantouvaki, M.; Guo, W.; Absil, P.; Van Campenhout, J.; Merckling, C.; Van Thourhout, D. Room-Temperature InP Distributed Feedback Laser Array Directly Grown on Silicon. Nat. Photonics 2015, 9, 837−842. (189) Carrad, D. J.; Mostert, A. B.; Ullah, A. R.; Burke, A. M.; Joyce, H. J.; Tan, H. H.; Jagadish, C.; Krogstrup, P.; Nygård, J.; Meredith, P.; et al. Hybrid Nanowire Ion-to-Electron Transducers for Integrated Bioelectronic Circuitry. Nano Lett. 2017, 17, 827−833. (190) Verardo, D.; Lindberg, F. W.; Anttu, N.; Niman, C. S.; Lard, M.; Dabkowska, A. P.; Nylander, T.; Månsson, A.; Prinz, C. N.; Linke, H. Nanowires for Biosensing: Lightguiding of Fluorescence as a Function of Diameter and Wavelength. Nano Lett. 2018, 18, 4796− 4802. (191) Piret, G.; Prinz, C. N. Could the Use of Nanowire Structures Overcome Some of the Current Limitations of Brain Electrode Implants? Nanomedicine 2016, 11, 745−747. (192) Tseng, A.; Lynall, D.; Savelyev, I.; Blumin, M.; Wang, S.; Ruda, H. Sensing Responses Based on Transfer Characteristics of InAs Nanowire Field-Effect Transistors. Sensors 2017, 17, 1640. (193) Zhang, X.; Fu, M.; Li, X.; Shi, T.; Ning, Z.; Wang, X.; Yang, T.; Chen, Q. Study on the Response of InAs Nanowire Transistors to H2O and NO2. Sens. Actuators, B 2015, 209, 456−461. (194) Upadhyay, S.; Frederiksen, R.; Lloret, N.; De Vico, L.; Krogstrup, P.; Jensen, J. H.; Martinez, K. L.; Nygård, J. Indium Arsenide Nanowire Field-Effect Transistors for PH and Biological Sensing. Appl. Phys. Lett. 2014, 104, 203504. (195) Chen, I.-J.; Burke, A.; Svilans, A.; Linke, H.; Thelander, C. Thermoelectric Power Factor Limit of a 1D Nanowire. Phys. Rev. Lett. 2018, 120, 177703. (196) Josefsson, M.; Svilans, A.; Burke, A. M.; Hoffmann, E. A.; Fahlvik, S.; Thelander, C.; Leijnse, M.; Linke, H. A Quantum-Dot Heat Engine Operating Close to the Thermodynamic Efficiency Limits. Nat. Nanotechnol. 2018, 13, 920. (197) Friedl, M.; Cerveny, K.; Weigele, P.; Tütüncüoglu, G.; MartíSánchez, S.; Huang, C.; Patlatiuk, T.; Potts, H.; Sun, Z.; Hill, M. O.; et al. Template-Assisted Scalable Nanowire Networks. Nano Lett. 2018, 18, 2666−2671. (198) del Alamo, J. A. Nanometre-Scale Electronics with III−V Compound Semiconductors. Nature 2011, 479, 317−323. (199) Riel, H.; Wernersson, L.-E.; Hong, M.; del Alamo, J. A. III−V Compound Semiconductor Transistorsfrom Planar to Nanowire Structures. MRS Bull. 2014, 39, 668−677. (200) Lind, E. High Frequency III−V Nanowire MOSFETs. Semicond. Sci. Technol. 2016, 31, 093005. (201) Ferain, I.; Colinge, C. A.; Colinge, J.-P. Multigate Transistors as the Future of Classical Metal−Oxide−Semiconductor Field-Effect Transistors. Nature 2011, 479, 310−316. (202) Del Alamo, J. A.; Antoniadis, D. A.; Lin, J.; Lu, W.; Vardi, A.; Zhao, X. Nanometer-Scale III-V MOSFETs. IEEE J. Electron Devices Soc. 2016, 4, 205−214. (203) Thelander, C.; Agarwal, P.; Brongersma, S.; Eymery, J.; Feiner, L. F.; Forchel, A.; Scheffler, M.; Riess, W.; Ohlsson, B. J.; Gösele, U.; et al. Nanowire-Based One-Dimensional Electronics. Mater. Today 2006, 9, 28−35. (204) Xiang, J.; Lu, W.; Hu, Y.; Wu, Y.; Yan, H.; Lieber, C. M. Ge/Si Nanowire Heterostructures as High-Performance Field-Effect Transistors. Nature 2006, 441, 489−493. (205) Bryllert, T.; Wernersson, L.; Froberg, L. E.; Samuelson, L. Vertical High-Mobility Wrap-Gated InAs Nanowire Transistor. IEEE Electron Device Lett. 2006, 27, 323−325. (206) Jiang, X.; Xiong, Q.; Nam, S.; Qian, F.; Li, Y.; Lieber, C. M. InAs/InP Radial Nanowire Heterostructures as High Electron Mobility Devices. Nano Lett. 2007, 7, 3214−3218. (207) Mårtensson, T.; Svensson, C. P. T.; Wacaser, B. A.; Larsson, M. W.; Seifert, W.; Deppert, K.; Gustafsson, A.; Wallenberg, L. R.; Samuelson, L. Epitaxial III−V Nanowires on Silicon. Nano Lett. 2004, 4, 1987−1990. AN


Chemical Reviews

Review

(208) Tomioka, K.; Fukui, T. Recent Progress in Integration of III− V Nanowire Transistors on Si Substrate by Selective-Area Growth. J. Phys. D: Appl. Phys. 2014, 47, 394001. (209) Jönsson, A.; Svensson, J.; Wernersson, L. A Self-Aligned GateLast Process Applied to All-III−V CMOS on Si. IEEE Electron Device Lett. 2018, 39, 935−938. (210) Thelander, C.; Rehnstedt, C.; Froberg, L. E.; Lind, E.; Martensson, T.; Caroff, P.; Lowgren, T.; Ohlsson, B. J.; Samuelson, L.; Wernersson, L. Development of a Vertical Wrap-Gated InAs FET. IEEE Trans. Electron Devices 2008, 55, 3030−3036. (211) Zhang, C.; Li, X. III−V Nanowire Transistors for Low-Power Logic Applications: A Review and Outlook. IEEE Trans. Electron Devices 2016, 63, 223−234. (212) Wernersson, L. Properties of III−V Nanowires: MOSFETs and TunnelFETs. In 2017 Joint International EUROSOI Workshop and International Conference on Ultimate Integration on Silicon (EUROSOIULIS); 2017; pp 99−100. (213) Wu, J.; Wernersson, L. 3-D Integrated Track-and-Hold Circuit Using InAs Nanowire MOSFETs and Capacitors. IEEE Electron Device Lett. 2016, 37, 851−854. (214) Hou, C. 1.1 A Smart Design Paradigm for Smart Chips. In 2017 IEEE International Solid-State Circuits Conference (ISSCC); 2017; pp 8−13. (215) Yakimets, D.; Eneman, G.; Schuddinck, P.; Bao, T. H.; Bardon, M. G.; Raghavan, P.; Veloso, A.; Collaert, N.; Mercha, A.; Verkest, D.; Thean, A. V.-Y.; De Meyer, K. Vertical GAAFETs for the Ultimate CMOS Scaling. IEEE Trans. Electron Devices 2015, 62, 1433−1439. (216) Kilpi, O.; Svensson, J.; Wernersson, L. Sub-100-Nm GateLength Scaling of Vertical InAs/InGaAs Nanowire MOSFETs on Si. In 2017 IEEE International Electron Devices Meeting (IEDM); 2017; pp 17.3.1−17.3.4. (217) Berg, M.; Persson, K.; Kilpi, O.; Svensson, J.; Lind, E.; Wernersson, L. Self-Aligned, Gate-Last Process for Vertical InAs Nanowire MOSFETs on Si. In 2015 IEEE International Electron Devices Meeting (IEDM); 2015; pp 31.2.1−31.2.4. (218) Schmid, H.; Borg, M.; Moselund, K.; Gignac, L.; Breslin, C. M.; Bruley, J.; Cutaia, D.; Riel, H. Template-Assisted Selective Epitaxy of III−V Nanoscale Devices for Co-Planar Heterogeneous Integration with Si. Appl. Phys. Lett. 2015, 106, 233101. (219) Storm, K.; Nylund, G.; Samuelson, L.; Micolich, A. P. Realizing Lateral Wrap-Gated Nanowire FETs: Controlling Gate Length with Chemistry Rather than Lithography. Nano Lett. 2012, 12, 1−6. (220) Li, Q.; Huang, S.; Pan, D.; Wang, J.; Zhao, J.; Xu, H. Q. Suspended InAs Nanowire Gate-All-around Field-Effect Transistors. Appl. Phys. Lett. 2014, 105, 113106. (221) Shen, L.-F.; Yip, S.; Yang, Z.; Fang, M.; Hung, T.; Pun, E. Y. B.; Ho, J. C. High-Performance Wrap-Gated InGaAs Nanowire FieldEffect Transistors with Sputtered Dielectrics. Sci. Rep. 2015, 5, 16871. (222) Zhang, C.; Choi, W.; Mohseni, P. K.; Li, X. InAs Planar Nanowire Gate-All-Around MOSFETs on GaAs Substrates by Selective Lateral Epitaxy. IEEE Electron Device Lett. 2015, 36, 663− 665. (223) Pastorek, M.; Olivier, A.; Lechaux, Y.; Wichmann, N.; Karatsori, T.; Fahed, M.; Bucamp, A.; Addad, A.; Troadec, D.; Ghibaudo, G.; et al. Bottom-up Fabrication of InAs-on-Nothing MOSFET Using Selective Area Molecular Beam Epitaxy. Nanotechnology 2019, 30, 035301. (224) Ghalamestani, S. G.; Johansson, S.; Borg, B. M.; Lind, E.; Dick, K. A.; Wernersson, L.-E. Uniform and Position-Controlled InAs Nanowires on 2 ” Si Substrates for Transistor Applications. Nanotechnology 2012, 23, 015302. (225) Berg, M.; Persson, K.-M.; Wu, J.; Lind, E.; Sjöland, H.; Wernersson, L.-E. InAs Nanowire MOSFETs in Three-Transistor Configurations: Single Balanced RF down-Conversion Mixers. Nanotechnology 2014, 25, 485203.

(226) Du, J.; Liang, D.; Tang, H.; Gao, X. P. A. InAs Nanowire Transistors as Gas Sensor and the Response Mechanism. Nano Lett. 2009, 9, 4348−4351. (227) Zota, C. B.; Lindelow, F.; Wernersson, L.; Lind, E. InGaAs Tri-Gate MOSFETs with Record on-Current. In 2016 IEEE International Electron Devices Meeting (IEDM); 2016; pp 3.2.1−3.2.4. (228) Gu, J. J.; Liu, Y. Q.; Wu, Y. Q.; Colby, R.; Gordon, R. G.; Ye, P. D. First Experimental Demonstration of Gate-All-around III−V MOSFETs by Top-down Approach. In 2011 International Electron Devices Meeting; 2011; pp 33.2.1−33.2.4. (229) Zhao, X.; Vardi, A.; del Alamo, J. A. Sub-Thermal Subthreshold Characteristics in Top−Down InGaAs/InAs Heterojunction Vertical Nanowire Tunnel FETs. IEEE Electron Device Lett. 2017, 38, 855−858. (230) Ramesh, S.; Ivanov, T.; Camerotto, E.; Sun, N.; Franco, J.; Sibaja-Hernandez, A.; Rooyackers, R.; Alian, A.; Loo, J.; Veloso, A.; et al. Top-down InGaAs Nanowire and Fin Vertical FETs with Record Performance. In 2016 IEEE Symposium on VLSI Technology; 2016; pp 1−2. (231) Goh, K.; Yadav, S.; Low, K. L.; Liang, G.; Gong, X.; Yeo, Y. Gate-All-Around In0.53Ga0.47As Junctionless Nanowire FET With Tapered Source/Drain Structure. IEEE Trans. Electron Devices 2016, 63, 1027−1033. (232) Doornbos, G.; Holland, M.; Vellianitis, G.; Van Dal, M. J. H.; Duriez, B.; Oxland, R.; Afzalian, A.; Chen, T.-K.; Hsieh, G.; Passlack, M.; Yeo, Y.-C. High-Performance InAs Gate-All-Around Nanowire MOSFETs on 300 Mm Si Substrates. IEEE J. Electron Devices Soc. 2016, 4, 253−259. (233) Waldron, N.; Sioncke, S.; Franco, J.; Nyns, L.; Vais, A.; Zhou, X.; Lin, H. C.; Boccardi, G.; Maes, J. W.; Xie, Q.; et al. Gate-Allaround InGaAs Nanowire FETS with Peak Transconductance of 2200μS/Μm at 50nm Lg Using a Replacement Fin RMG Flow. In 2015 IEEE International Electron Devices Meeting (IEDM); 2015; pp 31.1.1−31.1.4. (234) Vasen, T.; Ramvall, P.; Afzalian, A.; Thelander, C.; Dick, K. A.; Holland, M.; Doornbos, G.; Wang, S. W.; Oxland, R.; Vellianitis, G.; et al. InAs Nanowire GAA N-MOSFETs with 12−15 Nm Diameter. In 2016 IEEE Symposium on VLSI Technology; 2016; pp 1− 2. (235) Fu, M.; Pan, D.; Yang, Y.; Shi, T.; Zhang, Z.; Zhao, J.; Xu, H. Q.; Chen, Q. Electrical Characteristics of Field-Effect Transistors Based on Indium Arsenide Nanowire Thinner than 10 Nm. Appl. Phys. Lett. 2014, 105, 143101. (236) Zota, C. B.; Lind, E. Size-Effects in Indium Gallium Arsenide Nanowire Field-Effect Transistors. Appl. Phys. Lett. 2016, 109, 063505. (237) Li, T.; Shen, R.; Sun, M.; Pan, D.; Zhang, J.; Xu, J.; Zhao, J.; Chen, Q. Improving the Electrical Properties of InAs Nanowire Field Effect Transistors by Covering Them with Y2O3/HfO2 Layers. Nanoscale 2018, 10, 18492−18501. (238) Johansson, S.; Memisevic, E.; Wernersson, L.; Lind, E. HighFrequency Gate-All-Around Vertical InAs Nanowire MOSFETs on Si Substrates. IEEE Electron Device Lett. 2014, 35, 518−520. (239) Fu, M.; Tang, Z.; Li, X.; Ning, Z.; Pan, D.; Zhao, J.; Wei, X.; Chen, Q. Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires https://pubs.acs.org/doi/ full/10.1021/acs.nanolett.6b00045 (accessed Nov 1, 2018). (240) Kilpi, O.-P.; Svensson, J.; Wu, J.; Persson, A. R.; Wallenberg, R.; Lind, E.; Wernersson, L.-E. Vertical InAs/InGaAs Heterostructure Metal−Oxide−Semiconductor Field-Effect Transistors on Si. Nano Lett. 2017, 17, 6006−6010. (241) Zota, C. B.; Borg, M.; Wernersson, L.-E.; Lind, E. Junctionless Tri-Gate InGaAs MOSFETs. Jpn. J. Appl. Phys. 2017, 56, 120306. (242) Chen, Q.; Yang, W. (Invited) The Scaling-Down and Performance Optimization of InAs Nanowire Field Effect Transistors. ECS Trans. 2018, 86, 41−49. (243) Tomioka, K.; Fukui, T. (Invited) Transistor Applications Using Vertical III-V Nanowires on Si Platform. ECS Trans. 2017, 80, 43−52. AO


Chemical Reviews

Review

(263) Ionescu, A. M.; Riel, H. Tunnel Field-Effect Transistors as Energy-Efficient Electronic Switches. Nature 2011, 479, 329−337. (264) Lu, H.; Seabaugh, A. Tunnel Field-Effect Transistors: State-ofthe-Art. IEEE J. Electron Devices Soc. 2014, 2, 44−49. (265) Convertino, C.; Zota, C. B.; Schmid, H.; Ionescu, A. M.; Moselund, K. E. III-V Heterostructure Tunnel Field-Effect Transistor. J. Phys.: Condens. Matter 2018, 30, 264005. (266) Zhu, Y.; Hudait, M. K. Low-Power Tunnel Field Effect Transistors Using Mixed As and Sb Based Heterostructures. Nanotechnol. Rev. 2013, 2, 637−678. (267) Knoch, J. Nanowire Tunneling Field-Effect Transistors. In Semiconductors and Semimetals; Elsevier, 2016; Vol. 94, pp 273−295. (268) Tomioka, K.; Yoshimura, M.; Fukui, T. Steep-Slope Tunnel Field-Effect Transistors Using III−V Nanowire/Si Heterojunction. 2012 Symposium on VLSI Technology (VLSIT) 2012, 47−48. (269) Tomioka, K.; Yoshimura, M.; Fukui, T. Sub 60 MV/Decade Switch Using an InAs Nanowire−Si Heterojunction and Turn-on Voltage Shift with a Pulsed Doping Technique. Nano Lett. 2013, 13, 5822−5826. (270) Tomioka, K.; Yoshimura, M.; Nakai, E.; Ishizaka, F.; Fukui, T. Integration of III−V Nanowires on Si: From High-Performance Vertical FET to Steep-Slope Switch. In 2013 IEEE International Electron Devices Meeting; 2013; pp 4.1.1−4.1.4. (271) Tomioka, K.; Fukui, T. Current Increment of Tunnel FieldEffect Transistor Using InGaAs Nanowire/Si Heterojunction by Scaling of Channel Length. Appl. Phys. Lett. 2014, 104, 073507. (272) Dey, A. W.; Borg, B. M.; Ganjipour, B.; Ek, M.; Dick, K. A.; Lind, E.; Thelander, C.; Wernersson, L. High-Current GaSb/ InAs(Sb) Nanowire Tunnel Field-Effect Transistors. IEEE Electron Device Lett. 2013, 34, 211−213. (273) Cutaia, D.; Moselund, K. E.; Schmid, H.; Borg, M.; Olziersky, A.; Riel, H. Complementary III−V Heterojunction Lateral NW Tunnel FET Technology on Si. In 2016 IEEE Symposium on VLSI Technology; 2016; pp 1−2. (274) Memišević, E.; Svensson, J.; Hellenbrand, M.; Lind, E.; Wernersson, L. Scaling of Vertical InAs−GaSb Nanowire Tunneling Field-Effect Transistors on Si. IEEE Electron Device Lett. 2016, 37, 549−552. (275) Memisevic, E.; Svensson, J.; Lind, E.; Wernersson, L. InAs/ InGaAsSb/GaSb Nanowire Tunnel Field-Effect Transistors. IEEE Trans. Electron Devices 2017, 64, 4746−4751. (276) Memisevic, E.; Svensson, J.; Lind, E.; Wernersson, L. Vertical Nanowire TFETs With Channel Diameter Down to 10 Nm and Point SMINof 35 MV/Decade. IEEE Electron Device Lett. 2018, 39, 1089− 1091. (277) Ganjipour, B.; Wallentin, J.; Borgström, M. T.; Samuelson, L.; Thelander, C. Tunnel Field-Effect Transistors Based on InP-GaAs Heterostructure Nanowires. ACS Nano 2012, 6, 3109−3113. (278) Moselund, K. E.; Schmid, H.; Bessire, C.; Bjork, M. T.; Ghoneim, H.; Riel, H. InAs−Si Nanowire Heterojunction Tunnel FETs. IEEE Electron Device Lett. 2012, 33, 1453−1455. (279) Cutaia, D.; Moselund, K. E.; Borg, M.; Schmid, H.; Gignac, L.; Breslin, C. M.; Karg, S.; Uccelli, E.; Riel, H. Vertical InAs-Si Gate-AllAround Tunnel FETs Integrated on Si Using Selective Epitaxy in Nanotube Templates. IEEE J. Electron Devices Soc. 2015, 3, 176−183. (280) Moselund, K. E.; Cutaia, D.; Schmid, H.; Borg, M.; Sant, S.; Schenk, A.; Riel, H. Lateral InAs/Si p-Type Tunnel FETs Integrated on SiPart 1: Experimental Devices. IEEE Trans. Electron Devices 2016, 63, 4233−4239. (281) Knoch, J.; Appenzeller, J. Modeling of High-Performance pType III−V Heterojunction Tunnel FETs. IEEE Electron Device Lett. 2010, 31, 305−307. (282) Memisevic, E.; Hellenbrand, M.; Lind, E.; Persson, A. R.; Sant, S.; Schenk, A.; Svensson, J.; Wallenberg, R.; Wernersson, L.-E. Individual Defects in InAs/InGaAsSb/GaSb Nanowire Tunnel FieldEffect Transistors Operating below 60 MV/Decade. Nano Lett. 2017, 17, 4373−4380. (283) Schenk, A.; Sant, S.; Moselund, K., Riel, H. The Impact of Hetero-Junction and Oxide-Interface Traps on the Performance of

(244) Zhang, C.; Miao, X.; Chabak, K. D.; Li, X. A Review of III−V Planar Nanowire Arrays: Selective Lateral VLS Epitaxy and 3D Transistors. J. Phys. D: Appl. Phys. 2017, 50, 393001. (245) Blekker, K.; Munstermann, B.; Matiss, A.; Do, Q. T.; Regolin, I.; Brockerhoff, W.; Prost, W.; Tegude, F. High-Frequency Measurements on InAs Nanowire Field-Effect Transistors Using Coplanar Waveguide Contacts. IEEE Trans. Nanotechnol. 2010, 9, 432−437. (246) Zota, C. B.; Roll, G.; Wernersson, L.; Lind, E. RadioFrequency Characterization of Selectively Regrown InGaAs Lateral Nanowire MOSFETs. IEEE Trans. Electron Devices 2014, 61, 4078− 4083. (247) Miao, X.; Chabak, K.; Zhang, C.; Mohseni, P. K.; Walker, D.; Li, X. High-Speed Planar GaAs Nanowire Arrays with Fmax > 75 GHz by Wafer-Scale Bottom-up Growth. Nano Lett. 2015, 15, 2780−2786. (248) Appenzeller, J.; Knoch, J.; Bjork, M. T.; Riel, H.; Schmid, H.; Riess, W. Toward Nanowire Electronics. IEEE Trans. Electron Devices 2008, 55, 2827−2845. (249) Berg, M.; Svensson, J.; Lind, E.; Wernersson, L.-E. A Transmission Line Method for Evaluation of Vertical InAs Nanowire Contacts. Appl. Phys. Lett. 2015, 107, 232102. (250) Shi, T.; Fu, M.; Pan, D.; Guo, Y.; Zhao, J.; Chen, Q. Contact Properties of Field-Effect Transistors Based on Indium Arsenide Nanowires Thinner than 16 Nm. Nanotechnology 2015, 26, 175202. (251) Gluschke, J. G.; Seidl, J.; Lyttleton, R. W.; Carrad, D. J.; Cochrane, J. W.; Lehmann, S.; Samuelson, L.; Micolich, A. P. Using Ultrathin Parylene Films as an Organic Gate Insulator in Nanowire Field-Effect Transistors. Nano Lett. 2018, 18, 4431−4439. (252) Potts, H.; Friedl, M.; Amaduzzi, F.; Tang, K.; Tütüncüoglu, G.; Matteini, F.; Alarcon Lladó, E.; McIntyre, P. C.; Fontcuberta i Morral, A. From Twinning to Pure Zincblende Catalyst-Free InAs(Sb) Nanowires. Nano Lett. 2016, 16, 637−643. (253) Wang, F.; Yip, S.; Dong, G.; Xiu, F.; Song, L.; Yang, Z.; Li, D.; Hung, T. F.; Han, N.; Ho, J. C. Manipulating III−V Nanowire Transistor Performance via Surface Decoration of Metal-Oxide Nanoparticles. Adv. Mater. Interfaces 2017, 4, 1700260. (254) Yang, W.; Pan, D.; Shen, R.; Wang, X.; Zhao, J.; Chen, Q. Suppressing the Excess OFF-State Current of Short-Channel InAs Nanowire Field-Effect Transistors by Nanoscale Partial-Gate. Nanotechnology 2018, 29, 415203. (255) Memisevic, E.; Svensson, J.; Hellenbrand, M.; Lind, E.; Wernersson, L.-. Vertical InAs/GaAsSb/GaSb Tunneling Field-Effect Transistor on Si with S = 48 MV/Decade and Ion = 10 ΜA/Μm for Ioff = 1 NA/Μm at Vds = 0.3 V. In 2016 IEEE International Electron Devices Meeting (IEDM); 2016; pp 19.1.1−19.1.4. (256) Memišević, E.; Lind, E.; Wernersson, L.-E. Thin Electron Beam Defined Hydrogen Silsesquioxane Spacers for Vertical Nanowire Transistors. J. Vac. Sci. Technol., B: Nanotechnol. Microelectron.: Mater., Process., Meas., Phenom. 2014, 32, 051211. (257) Kilpi, O.; Wu, J.; Svensson, J.; Lind, E.; Wernersson, L. Vertical Heterojunction InAs/InGaAs Nanowire MOSFETs on Si with Io n= 330 ΜA/Μm at Ioff = 100 NA/Μm and VD = 0.5 V. In 2017 Symposium on VLSI Technology; 2017; pp T36−T37. (258) Babadi, A. S.; Svensson, J.; Lind, E.; Wernersson, L.-E. Impact of Doping and Diameter on the Electrical Properties of GaSb Nanowires. Appl. Phys. Lett. 2017, 110, 053502. (259) Yang, Z.; Yip, S.; Li, D.; Han, N.; Dong, G.; Liang, X.; Shu, L.; Hung, T. F.; Mo, X.; Ho, J. C. Approaching the Hole Mobility Limit of GaSb Nanowires. ACS Nano 2015, 9, 9268−9275. (260) Borg, B. M.; Wernersson, L.-E. Synthesis and Properties of Antimonide Nanowires. Nanotechnology 2013, 24, 202001. (261) Lu, W.; Roh, I. P.; Geum, D.; Kim, S.; Song, J. D.; Kong, L.; Alamo, J. A. del. 10-Nm Fin-Width InGaSb p-Channel Self-Aligned FinFETs Using Antimonide-Compatible Digital Etch. In 2017 IEEE International Electron Devices Meeting (IEDM); 2017; pp 17.7.1− 17.7.4. (262) Ullah, A. R.; Meyer, F.; Gluschke, J. G.; Naureen, S.; Caroff, P.; Krogstrup, P.; Nygård, J.; Micolich, A. P. P-GaAs Nanowire Metal−Semiconductor Field-Effect Transistors with Near-Thermal Limit Gating. Nano Lett. 2018, 18, 5673−5680. AP


Chemical Reviews

Review

InAs/Si Tunnel FETs2017 17th International Workshop on Junction Technology (IWJT)20172730 (284) Sant, S.; Moselund, K.; Cutaia, D.; Schmid, H.; Borg, M.; Riel, H.; Schenk, A. Lateral InAs/Si p-Type Tunnel FETs Integrated on SiPart 2: Simulation Study of the Impact of Interface Traps. IEEE Trans. Electron Devices 2016, 63, 4240−4247. (285) Sant, S.; Schenk, A.; Moselund, K.; Riel, H. Impact of TrapAssisted Tunneling and Channel Quantization on InAs/Si Hetero Tunnel FETs. In 2016 74th Annual Device Research Conference (DRC); 2016; pp 1−2. (286) Wang, J.; Gudiksen, M. S.; Duan, X.; Cui, Y.; Lieber, C. M. Highly Polarized Photoluminescence and Photodetection from Single Indium Phosphide Nanowires. Science 2001, 293, 1455−1457. (287) Soci, C.; Zhang, A.; Bao, X.-Y.; Kim, H.; Lo, Y.; Wang, D. Nanowire Photodetectors http://www.ingentaconnect.com/content/ asp/jnn/2010/00000010/00000003/art00003 (accessed Nov 4, 2018). (288) Shen, L.; Pun, E. Y. B.; Ho, J. C. Recent Developments in III− V Semiconducting Nanowires for High-Performance Photodetectors. Mater. Chem. Front. 2017, 1, 630−645. (289) Kind, H.; Yan, H.; Messer, B.; Law, M.; Yang, P. Nanowire Ultraviolet Photodetectors and Optical Switches. Adv. Mater. 2002, 14, 158−160. (290) Soci, C.; Zhang, A.; Xiang, B.; Dayeh, S. A.; Aplin, D. P. R.; Park, J.; Bao, X. Y.; Lo, Y. H.; Wang, D. ZnO Nanowire UV Photodetectors with High Internal Gain. Nano Lett. 2007, 7, 1003− 1009. (291) Zhuge, F.; Zheng, Z.; Luo, P.; Lv, L.; Huang, Y.; Li, H.; Zhai, T. Nanostructured Materials and Architectures for Advanced Infrared Photodetection. Adv. Mater. Technol. 2017, 2, 1700005. (292) LaPierre, R. R.; Robson, M.; Azizur-Rahman, K. M.; Kuyanov, P. A Review of III−V Nanowire Infrared Photodetectors and Sensors. J. Phys. D: Appl. Phys. 2017, 50, 123001. (293) Monemar, B.; Ohlsson, B. J.; Gardner, N. F.; Samuelson, L. Chapter Seven - Nanowire-Based Visible Light Emitters, Present Status and Outlook. In Semiconductors and Semimetals; Semiconductor Nanowires II: Properties and Applications; Dayeh, S. A., Fontcuberta i Morral, A., Jagadish, C., Eds. Elsevier, 2016; Vol. 94, pp 227−271. (294) Rogalski, A. History of Infrared Detectors. Opto-Electron. Rev. 2012, 20, 279−308. (295) Dai, X.; Tchernycheva, M.; Soci, C. Compound Semiconductor Nanowire Photodetectors. In Semiconductors and Semimetals; Elsevier, 2016; Vol. 94, pp 75−107. (296) Liang, F.-X.; Wang, J.-Z.; Li, Z.-P.; Luo, L.-B. Near-InfraredLight Photodetectors Based on One-Dimensional Inorganic Semiconductor Nanostructures. Adv. Opt. Mater. 2017, 5, 1700081. (297) Sun, J.; Han, M.; Gu, Y.; Yang, Z.; Zeng, H. Recent Advances in Group III−V Nanowire Infrared Detectors. Adv. Opt. Mater. 2018, 6, 1800256. (298) Zhao, C.; Alfaraj, N.; Chandra Subedi, R.; Liang, J. W.; Alatawi, A. A.; Alhamoud, A. A.; Ebaid, M.; Alias, M. S.; Ng, T. K.; Ooi, B. S. III-Nitride Nanowires on Unconventional Substrates: From Materials to Optoelectronic Device Applications. Prog. Quantum Electron. 2018, 61, 1−31. (299) Zhao, S.; Nguyen, H. P. T.; Kibria, Md. G.; Mi, Z. III-Nitride Nanowire Optoelectronics. Prog. Quantum Electron. 2015, 44, 14−68. (300) Zou, Y.; Zhang, Y.; Hu, Y.; Gu, H. Ultraviolet Detectors Based on Wide Bandgap Semiconductor Nanowire: A Review. Sensors 2018, 18, 2072. (301) Ma, L.; Zhang, X.; Li, H.; Tan, H.; Yang, Y.; Xu, Y.; Hu, W.; Zhu, X.; Zhuang, X.; Pan, A. Bandgap-Engineered GaAsSb Alloy Nanowires for near-Infrared Photodetection at 1.31 μ m. Semicond. Sci. Technol. 2015, 30, 105033. (302) Tan, H.; Fan, C.; Ma, L.; Zhang, X.; Fan, P.; Yang, Y.; Hu, W.; Zhou, H.; Zhuang, X.; Zhu, X.; et al. Single-Crystalline InGaAs Nanowires for Room-Temperature High-Performance Near-Infrared Photodetectors. Nano-Micro Lett. 2016, 8, 29−35. (303) Zheng, D.; Wang, J.; Hu, W.; Liao, L.; Fang, H.; Guo, N.; Wang, P.; Gong, F.; Wang, X.; Fan, Z.; et al. When Nanowires Meet

Ultrahigh Ferroelectric Field−High-Performance Full-Depleted Nanowire Photodetectors. Nano Lett. 2016, 16, 2548−2555. (304) Miao, J.; Hu, W.; Guo, N.; Lu, Z.; Zou, X.; Liao, L.; Shi, S.; Chen, P.; Fan, Z.; Ho, J. C.; et al. Single InAs Nanowire RoomTemperature Near-Infrared Photodetectors. ACS Nano 2014, 8, 3628−3635. (305) Guo, N.; Hu, W.; Liao, L.; Yip, S.; Ho, J. C.; Miao, J.; Zhang, Z.; Zou, J.; Jiang, T.; Wu, S.; et al. Anomalous and Highly Efficient InAs Nanowire Phototransistors Based on Majority Carrier Transport at Room Temperature. Adv. Mater. 2014, 26, 8203−8209. (306) Yang, Y.; Peng, X.; Kim, H.-S.; Kim, T.; Jeon, S.; Kang, H. K.; Choi, W.; Song, J.; Doh, Y.-J.; Yu, D. Hot Carrier Trapping Induced Negative Photoconductance in InAs Nanowires toward Novel Nonvolatile Memory. Nano Lett. 2015, 15, 5875−5882. (307) Fang, H.; Hu, W.; Wang, P.; Guo, N.; Luo, W.; Zheng, D.; Gong, F.; Luo, M.; Tian, H.; Zhang, X.; et al. Visible Light-Assisted High-Performance Mid-Infrared Photodetectors Based on Single InAs Nanowire. Nano Lett. 2016, 16, 6416−6424. (308) Zhou, C.; Zhang, X.-T.; Zheng, K.; Chen, P.-P.; Lu, W.; Zou, J. Self-Assembly Growth of In-Rich InGaAs Core−Shell Structured Nanowires with Remarkable Near-Infrared Photoresponsivity. Nano Lett. 2017, 17, 7824−7830. (309) Chen, X.; Xia, N.; Yang, Z.; Gong, F.; Wei, Z.; Wang, D.; Tang, J.; Fang, X.; Fang, D.; Liao, L. Analysis of the Influence and Mechanism of Sulfur Passivation on the Dark Current of a Single GaAs Nanowire Photodetector. Nanotechnology 2018, 29, 095201. (310) Dai, X.; Zhang, S.; Wang, Z.; Adamo, G.; Liu, H.; Huang, Y.; Couteau, C.; Soci, C. GaAs/AlGaAs Nanowire Photodetector. Nano Lett. 2014, 14, 2688−2693. (311) Yan, X.; Li, B.; Wu, Y.; Zhang, X.; Ren, X. A Single Crystalline InP Nanowire Photodetector. Appl. Phys. Lett. 2016, 109, 053109. (312) Duan, T.; Liao, C.; Chen, T.; Yu, N.; Liu, Y.; Yin, H.; Xiong, Z.-J.; Zhu, M.-Q. Single Crystalline Nitrogen-Doped InP Nanowires for Low-Voltage Field-Effect Transistors and Photodetectors on Rigid Silicon and Flexible Mica Substrates. Nano Energy 2015, 15, 293−302. (313) Chen, G.; Liang, B.; Liu, Z.; Yu, G.; Xie, X.; Luo, T.; Xie, Z.; Chen, D.; Zhu, M.-Q.; Shen, G. High Performance Rigid and Flexible Visible-Light Photodetectors Based on Aligned X(In, Ga)P Nanowire Arrays. J. Mater. Chem. C 2014, 2, 1270−1277. (314) Li, Z.; Yuan, X.; Fu, L.; Peng, K.; Wang, F.; Fu, X.; Caroff, P.; White, T. P.; Tan, H. H.; Jagadish, C. Room Temperature GaAsSb Single Nanowire Infrared Photodetectors. Nanotechnology 2015, 26, 445202. (315) Huh, J.; Yun, H.; Kim, D.-C.; Munshi, A. M.; Dheeraj, D. L.; Kauko, H.; van Helvoort, A. T. J.; Lee, S.; Fimland, B.-O.; Weman, H. Rectifying Single GaAsSb Nanowire Devices Based on Self-Induced Compositional Gradients. Nano Lett. 2015, 15, 3709−3715. (316) Ma, L.; Hu, W.; Zhang, Q.; Ren, P.; Zhuang, X.; Zhou, H.; Xu, J.; Li, H.; Shan, Z.; Wang, X.; et al. Room-Temperature Near-Infrared Photodetectors Based on Single Heterojunction Nanowires. Nano Lett. 2014, 14, 694−698. (317) Ren, P.; Hu, W.; Zhang, Q.; Zhu, X.; Zhuang, X.; Ma, L.; Fan, X.; Zhou, H.; Liao, L.; Duan, X.; et al. Band-Selective Infrared Photodetectors with Complete-Composition-Range InAsxP1-x Alloy Nanowires. Adv. Mater. 2014, 26, 7444−7449. (318) Ren, D.; Meng, X.; Rong, Z.; Cao, M.; Farrell, A. C.; Somasundaram, S.; Azizur-Rahman, K. M.; Williams, B. S.; Huffaker, D. L. Uncooled Photodetector at Short-Wavelength Infrared Using InAs Nanowire Photoabsorbers on InP with p−n Heterojunctions. Nano Lett. 2018, 18, 7901−7908. (319) Shin, H. W.; Lee, S. J.; Kim, D. G.; Bae, M.-H.; Heo, J.; Choi, K. J.; Choi, W. J.; Choe, J.; Shin, J. C. Short-Wavelength Infrared Photodetector on Si Employing Strain-Induced Growth of Very Tall InAs Nanowire Arrays. Sci. Rep. 2015, 5, 10764. (320) Lee, W.-J.; Senanayake, P.; Farrell, A. C.; Lin, A.; Hung, C.-H.; Huffaker, D. L. High Quantum Efficiency Nanopillar Photodiodes Overcoming the Diffraction Limit of Light. Nano Lett. 2016, 16, 199− 204. AQ


Chemical Reviews

Review

Toward Single-Photon Detection in Free-Running Mode. Nano Lett. 2019, 19, 582−590. (340) Svensson, C. P. T.; Mårtensson, T.; Trägårdh, J.; Larsson, C.; Rask, M.; Hessman, D.; Samuelson, L.; Ohlsson, J. Monolithic GaAs/ InGaP Nanowire Light Emitting Diodes on Silicon. Nanotechnology 2008, 19, 305201. (341) Kawaguchi, K.; Sudo, H.; Matsuda, M.; Ekawa, M.; Yamamoto, T.; Arakawa, Y. Room-Temperature Electroluminescence from Radial p−i−n InP/InAsP/InP Nanowire Heterostructures in the 1.5-Μm-Wavelength Region. Jpn. J. Appl. Phys. 2015, 54, 04DN02. (342) Kivisaari, P.; Berg, A.; Karimi, M.; Storm, K.; Limpert, S.; Oksanen, J.; Samuelson, L.; Pettersson, H.; Borgström, M. T. Optimization of Current Injection in AlGaInP Core−Shell Nanowire Light-Emitting Diodes. Nano Lett. 2017, 17, 3599−3606. (343) Ishizaka, F.; Hiraya, Y.; Tomioka, K.; Motohisa, J.; Fukui, T. Growth of All-Wurtzite InP/AlInP Core−Multishell Nanowire Array. Nano Lett. 2017, 17, 1350−1355. (344) Deshpande, S.; Bhattacharya, I.; Malheiros-Silveira, G.; Ng, K. W.; Schuster, F.; Mantei, W.; Cook, K.; Chang-Hasnain, C. Ultracompact Position-Controlled InP Nanopillar LEDs on Silicon with Bright Electroluminescence at Telecommunication Wavelengths. ACS Photonics 2017, 4, 695−702. (345) Malheiros-Silveira, G. N.; Lu, F.; Bhattacharya, I.; Tran, T.-T. D.; Sun, H.; Chang-Hasnain, C. J. III−V Compound Semiconductor Nanopillars Monolithically Integrated to Silicon Photonics. ACS Photonics 2017, 4, 1021−1025. (346) Giuntoni, I.; Geelhaar, L.; Bruns, J.; Riechert, H. Light Coupling between Vertical III-As Nanowires and Planar Si Photonic Waveguides for the Monolithic Integration of Active Optoelectronic Devices on a Si Platform. Opt. Express 2016, 24, 18417−18427. (347) Kurtz, S.; Haegel, N.; Sinton, R.; Margolis, R. A New Era for Solar. Nat. Photonics 2017, 11, 3−5. (348) Haegel, N. M.; Margolis, R.; Buonassisi, T.; Feldman, D.; Froitzheim, A.; Garabedian, R.; Green, M.; Glunz, S.; Henning, H.M.; Holder, B.; et al. Terawatt-Scale Photovoltaics: Trajectories and Challenges. Science 2017, 356, 141−143. (349) Garnett, E. C.; Brongersma, M. L.; Cui, Y.; McGehee, M. D. Nanowire Solar Cells. Annu. Rev. Mater. Res. 2011, 41, 269−295. (350) Fan, Z.; Ruebusch, D. J.; Rathore, A. A.; Kapadia, R.; Ergen, O.; Leu, P. W.; Javey, A. Challenges and Prospects of NanopillarBased Solar Cells. Nano Res. 2009, 2, 829. (351) Yu, Y.; Wang, X. Semiconductor Nanowires for Energy Harvesting. In Semiconductors and Semimetals; Elsevier, 2016; Vol. 94, pp 297−368. (352) Goodnick, S. M. Nanotechnology Pathways to NextGeneration Photovoltaics. In Semiconductor Nanotechnology; Nanostructure Science and Technology; Springer, Cham, 2018; pp 1−36. (353) Beard, M. C.; Luther, J. M.; Nozik, A. J. The Promise and Challenge of Nanostructured Solar Cells. Nat. Nanotechnol. 2014, 9, 951−954. (354) Borgstrom, M. T.; Magnusson, M. H.; Dimroth, F.; Siefer, G.; Hohn, O.; Riel, H.; Schmid, H.; Wirths, S.; Bjork, M.; Aberg, I.; Peijnenburg, W.; Vijver, M.; Tchernycheva, M.; Piazza, V.; Samuelson, L. Towards Nanowire Tandem Junction Solar Cells on Silicon. IEEE J. Photovolt. 2018, 8, 733−740. (355) Haight, R.; Haensch, W.; Friedman, D. Solar-Powering the Internet of Things. Science 2016, 353, 124−125. (356) Espinet-Gonzalez, P.; Barrigon, E.; Chen, Y.; Otnes, G.; Vescovi, G.; Mann, C.; Lloyd, J. V.; Walker, D.; Kelzenberg, M. D.; Aberg, I.; Borgstrom, M.; Samuelson, L.; Atwater, H. A. Nanowire Solar Cells: A New Radiation Hard PV Technology for Space Applications. 46th IEEE Photovoltaic Specialists Conference, 2019, Chicago USA. (357) Martí, A.; Araújo, G. L. Limiting Efficiencies for Photovoltaic Energy Conversion in Multigap Systems. Sol. Energy Mater. Sol. Cells 1996, 43, 203−222. (358) Shockley, W.; Queisser, H. J. Detailed Balance Limit of Efficiency of P-n Junction Solar Cells. J. Appl. Phys. 1961, 32, 510− 519.

(321) Thompson, M. D.; Alhodaib, A.; Craig, A. P.; Robson, A.; Aziz, A.; Krier, A.; Svensson, J.; Wernersson, L.-E.; Sanchez, A. M.; Marshall, A. R. J. Low Leakage-Current InAsSb Nanowire Photodetectors on Silicon. Nano Lett. 2016, 16, 182−187. (322) Wu, Y.; Yan, X.; Zhang, X.; Ren, X. A Monolayer Graphene/ GaAs Nanowire Array Schottky Junction Self-Powered Photodetector. Appl. Phys. Lett. 2016, 109, 183101. (323) Sharma, M.; Ahmad, E.; Dev, D.; Li, J.; Reynolds, C. L., Jr.; Liu, Y.; Iyer, S. Improved Performance of GaAsSb/AlGaAs Nanowire Ensemble Schottky Barrier Based Photodetector via in Situ Annealing. Nanotechnology 2019, 30, 034005. (324) Karimi, M.; Heurlin, M.; Limpert, S.; Jain, V.; Zeng, X.; Geijselaers, I.; Nowzari, A.; Fu, Y.; Samuelson, L.; Linke, H.; et al. Intersubband Quantum Disc-in-Nanowire Photodetectors with Normal-Incidence Response in the Long-Wavelength Infrared. Nano Lett. 2018, 18, 365−372. (325) Kuyanov, P.; McNamee, S. A.; LaPierre, R. R. GaAs Quantum Dots in a GaP Nanowire Photodetector. Nanotechnology 2018, 29, 124003. (326) Ren, D.; Rong, Z.; Azizur-Rahman, K. M.; Somasundaram, S.; Shahili, M.; Huffaker, D. L. Feasibility of Achieving High Detectivity at Short- and Mid-Wavelength Infrared Using Nanowire-Plasmonic Photodetectors with p−n Heterojunctions. Nanotechnology 2019, 30, 044002. (327) Svensson, J.; Anttu, N.; Vainorius, N.; Borg, B. M.; Wernersson, L.-E. Diameter-Dependent Photocurrent in InAsSb Nanowire Infrared Photodetectors. Nano Lett. 2013, 13, 1380−1385. (328) Svensson, J.; Chen, Y.; Anttu, N.; Pistol, M.-E.; Wernersson, L.-E. Increased Absorption in InAsSb Nanowire Clusters through Coupled Optical Modes. Appl. Phys. Lett. 2017, 110, 081104. (329) Jain, V.; Heurlin, M.; Barrigon, E.; Bosco, L.; Nowzari, A.; Shroff, S.; Boix, V.; Karimi, M.; Jam, R. J.; Berg, A.; et al. InP/InAsP Nanowire-Based Spatially Separate Absorption and Multiplication Avalanche Photodetectors. ACS Photonics 2017, 4, 2693−2698. (330) Fang, H.; Hu, W. Photogating in Low Dimensional Photodetectors. Adv. Sci. 2017, 4, 1700323. (331) Han, Y.; Zheng, X.; Fu, M.; Pan, D.; Li, X.; Guo, Y.; Zhao, J.; Chen, Q. Negative Photoconductivity of InAs Nanowires. Phys. Chem. Chem. Phys. 2016, 18, 818−826. (332) Li, J.; Yan, X.; Sun, F.; Zhang, X.; Ren, X. Anomalous Photoconductive Behavior of a Single InAs Nanowire Photodetector. Appl. Phys. Lett. 2015, 107, 263103. (333) Li, H.; Alradhi, H.; Jin, Z.; Anyebe, E. A.; Sanchez, A. M.; Linhart, W. M.; Kudrawiec, R.; Fang, H.; Wang, Z.; Hu, W.; et al. Novel Type-II InAs/AlSb Core−Shell Nanowires and Their Enhanced Negative Photocurrent for Efficient Photodetection. Adv. Funct. Mater. 2018, 28, 1705382. (334) Han, Y.; Fu, M.; Tang, Z.; Zheng, X.; Ji, X.; Wang, X.; Lin, W.; Yang, T.; Chen, Q. Switching from Negative to Positive Photoconductivity toward Intrinsic Photoelectric Response in InAs Nanowire. ACS Appl. Mater. Interfaces 2017, 9, 2867−2874. (335) Alexander-Webber, J. A.; Groschner, C. K.; Sagade, A. A.; Tainter, G.; Gonzalez-Zalba, M. F.; Di Pietro, R.; Wong-Leung, J.; Tan, H. H.; Jagadish, C.; Hofmann, S.; et al. Engineering the Photoresponse of InAs Nanowires. ACS Appl. Mater. Interfaces 2017, 9, 43993−44000. (336) Yang, C.; Barrelet, C. J.; Capasso, F.; Lieber, C. M. Single PType/Intrinsic/n-Type Silicon Nanowires as Nanoscale Avalanche Photodetectors. Nano Lett. 2006, 6, 2929−2934. (337) Hayden, O.; Agarwal, R.; Lieber, C. M. Nanoscale Avalanche Photodiodes for Highly Sensitive and Spatially Resolved Photon Detection. Nat. Mater. 2006, 5, 352−356. (338) Farrell, A. C.; Senanayake, P.; Hung, C.-H.; El-Howayek, G.; Rajagopal, A.; Currie, M.; Hayat, M. M.; Huffaker, D. L. Plasmonic Field Confinement for Separate Absorption-Multiplication in InGaAs Nanopillar Avalanche Photodiodes. Sci. Rep. 2015, 5, 17580. (339) Farrell, A. C.; Meng, X.; Ren, D.; Kim, H.; Senanayake, P.; Hsieh, N. Y.; Rong, Z.; Chang, T.-Y.; Azizur-Rahman, K. M.; Huffaker, D. L. InGaAs−GaAs Nanowire Avalanche Photodiodes AR


Chemical Reviews

Review

(359) Dimroth, F.; Tibbits, T. N. D.; Niemeyer, M.; Predan, F.; Beutel, P.; Karcher, C.; Oliva, E.; Siefer, G.; Lackner, D.; FusKailuweit, P.; Bett, A. W.; Krause, R.; Drazek, C.; Guiot, E.; Wasselin, J.; Tauzin, A.; Signamarcheix, T. Four-Junction Wafer-Bonded Concentrator Solar Cells. IEEE J. Photovolt. 2016, 6, 343−349. (360) LaPierre, R. R.; Chia, A. C. E.; Gibson, S. J.; Haapamaki, C. M.; Boulanger, J.; Yee, R.; Kuyanov, P.; Zhang, J.; Tajik, N.; Jewell, N.; et al. III−V Nanowire Photovoltaics: Review of Design for High Efficiency. Phys. Status Solidi RRL 2013, 7, 815−830. (361) Anttu, N.; Xu, H. Q. Efficient Light Management in Vertical Nanowire Arrays for Photovoltaics. Opt. Express 2013, 21, A558− A575. (362) Anttu, N. Shockley−Queisser Detailed Balance Efficiency Limit for Nanowire Solar Cells. ACS Photonics 2015, 2, 446−453. (363) Haverkort, J. E. M.; Garnett, E. C.; Bakkers, E. P. A. M. Fundamentals of the Nanowire Solar Cell: Optimization of the Open Circuit Voltage. Appl. Phys. Rev. 2018, 5, 031106. (364) Anttu, N.; Abrand, A.; Asoli, D.; Heurlin, M.; Åberg, I.; Samuelson, L.; Borgström, M. Absorption of Light in InP Nanowire Arrays. Nano Res. 2014, 7, 816−823. (365) van Dam, D.; van Hoof, N. J. J.; Cui, Y.; van Veldhoven, P. J.; Bakkers, E. P. A. M.; Gómez Rivas, J.; Haverkort, J. E. M. HighEfficiency Nanowire Solar Cells with Omnidirectionally Enhanced Absorption Due to Self-Aligned Indium−Tin−Oxide Mie Scatterers. ACS Nano 2016, 10, 11414−11419. (366) Otnes, G.; Borgström, M. T. Towards High Efficiency Nanowire Solar Cells. Nano Today 2017, 12, 31−45. (367) Standing, A. J.; Assali, S.; Haverkort, J. E. M.; Bakkers, E. P. A. M. High Yield Transfer of Ordered Nanowire Arrays into Transparent Flexible Polymer Films. Nanotechnology 2012, 23, 495305. (368) Chen, M.; Nakai, E.; Tomioka, K.; Fukui, T. Application of Free-Standing InP Nanowire Arrays and Their Optical Properties for Resource-Saving Solar Cells. Appl. Phys. Express 2015, 8, 012301. (369) Cavalli, A.; Dijkstra, A.; Haverkort, J. E. M.; Bakkers, E. P. A. M. Nanowire Polymer Transfer for Enhanced Solar Cell Performance and Lower Cost. Nano-Struct. Nano-Objects 2018, 16, 59−62. (370) Han, N.; Yang, Z.; Shen, L.; Lin, H.; Wang, Y.; Pun, E. Y. B.; Chen, Y.; Ho, J. C. Design and Fabrication of 1-D Semiconductor Nanomaterials for High-Performance Photovoltaics. Sci. Bull. 2016, 61, 357−367. (371) Mokkapati, S.; Jagadish, C. Review on Photonic Properties of Nanowires for Photovoltaics [Invited]. Opt. Express 2016, 24, 17345− 17358. (372) Wang, Y.; Zhou, X.; Yang, Z.; Wang, F.; Han, N.; Chen, Y.; Ho, J. C. GaAs Nanowires Grown by Catalyst Epitaxy for High Performance Photovoltaics. Crystals 2018, 8, 347. (373) Li, Z.; Tan, H. H.; Jagadish, C.; Fu, L. III−V Semiconductor Single Nanowire Solar Cells: A Review. Adv. Mater. Technol. 2018, 3, 1800005. (374) Borgström, M. T.; Wallentin, J.; Heurlin, M.; Fält, S.; Wickert, P.; Leene, J.; Magnusson, M. H.; Deppert, K.; Samuelson, L. Nanowires With Promise for Photovoltaics. IEEE J. Sel. Top. Quantum Electron. 2011, 17, 1050−1061. (375) Wood, B. A.; Kuyanov, P.; Aagesen, M.; LaPierre, R. R. GaAsP Nanowire-on-Si Tandem Solar Cell. J. Photonics Energy 2017, 7, 042502. (376) Mohseni, P. K.; Behnam, A.; Wood, J. D.; Zhao, X.; Yu, K. J.; Wang, N. C.; Rockett, A.; Rogers, J. A.; Lyding, J. W.; Pop, E.; et al. Monolithic III-V Nanowire Solar Cells on Graphene via Direct van Der Waals Epitaxy. Adv. Mater. 2014, 26, 3755−3760. (377) Gao, Q.; Li, Z.; Li, L.; Vora, K.; Li, Z.; Alabadla, A.; Wang, F.; Guo, Y.; Peng, K.; Wenas, Y. C.; et al. Axial P-n Junction Design and Characterization for InP Nanowire Array Solar Cells. Prog. Photovoltaics 2019, 27, 237−244. (378) Nowzari, A.; Heurlin, M.; Jain, V.; Storm, K.; Hosseinnia, A.; Anttu, N.; Borgström, M. T.; Pettersson, H.; Samuelson, L. A Comparative Study of Absorption in Vertically and Laterally Oriented InP Core−Shell Nanowire Photovoltaic Devices. Nano Lett. 2015, 15, 1809−1814.

(379) Sturmberg, B. C. P.; Dossou, K. B.; Botten, L. C.; Asatryan, A. A.; Poulton, C. G.; McPhedran, R. C.; de Sterke, C. M. Optimizing Photovoltaic Charge Generation of Nanowire Arrays: A Simple SemiAnalytic Approach. ACS Photonics 2014, 1, 683−689. (380) Wang, X.; Khan, M. R.; Lundstrom, M.; Bermel, P. Performance-Limiting Factors for GaAs-Based Single Nanowire Photovoltaics. Opt. Express 2014, 22, A344−A358. (381) Li, Z.; Wenas, Y. C.; Fu, L.; Mokkapati, S.; Tan, H. H.; Jagadish, C. Influence of Electrical Design on Core−Shell GaAs Nanowire Array Solar Cells. IEEE J. Photovolt. 2015, 5, 854−864. (382) Xu, Y.; Gong, T.; Munday, J. N. The Generalized ShockleyQueisser Limit for Nanostructured Solar Cells. Sci. Rep. 2015, 5, 13536. (383) Trojnar, A. H.; Valdivia, C. E.; LaPierre, R. R.; Hinzer, K.; Krich, J. J. Optimizations of GaAs Nanowire Solar Cells. IEEE J. Photovolt. 2016, 6, 1494−1501. (384) Wang, Y.; Zhang, X.; Sun, X.; Qi, Y.; Wang, Z.; Wang, H. Enhanced Optical Properties in Inclined GaAs Nanowire Arrays for High-Efficiency Solar Cells. Opt. Laser Technol. 2016, 85, 85−90. (385) Zeng, Y.; Ye, Q.; Shen, W. Design of Coated Standing Nanowire Array Solar Cell Performing beyond the Planar Efficiency Limits. J. Appl. Phys. 2016, 119, 203108. (386) Wu, D.; Tang, X.; Wang, K.; Li, X. An Analytic Approach for Optimal Geometrical Design of GaAs Nanowires for Maximal Light Harvesting in Photovoltaic Cells. Sci. Rep. 2017, 7, 46504. (387) Hill, D. J.; Teitsworth, T. S.; Ritchie, E. T.; Atkin, J. M.; Cahoon, J. F. Interplay of Surface Recombination and Diode Geometry for the Performance of Axial p−i−n Nanowire Solar Cells. ACS Nano 2018, 12, 10554−10563. (388) Wu, Y.; Yan, X.; Wei, W.; Zhang, J.; Zhang, X.; Ren, X. Optimization of GaAs Nanowire Pin Junction Array Solar Cells by Using AlGaAs/GaAs Heterojunctions. Nanoscale Res. Lett. 2018, 13, 126. (389) Li, X.; Shi, T.; Liu, G.; Wen, L.; Zhou, B.; Wang, Y. Absorption Enhancement of GaInP Nanowires by Tailoring Transparent Shell Thicknesses and Its Application in III-V Nanowire/Si Film Two-Junction Solar Cells. Opt. Express 2015, 23, 25316−25328. (390) Chen, Y.; Kivisaari, P.; Pistol, M.-E.; Anttu, N. Optimization of the Short-Circuit Current in an InP Nanowire Array Solar Cell through Opto-Electronic Modeling. Nanotechnology 2016, 27, 435404. (391) Mann, S. A.; Grote, R. R.; Osgood, R. M.; Alù, A.; Garnett, E. C. Opportunities and Limitations for Nanophotonic Structures To Exceed the Shockley−Queisser Limit. ACS Nano 2016, 10, 8620− 8631. (392) Mann, S. A.; Oener, S. Z.; Cavalli, A.; Haverkort, J. E. M.; Bakkers, E. P. A. M.; Garnett, E. C. Quantifying Losses and Thermodynamic Limits in Nanophotonic Solar Cells. Nat. Nanotechnol. 2016, 11, 1071. (393) Chen, Y.; Kivisaari, P.; Pistol, M.; Anttu, N. One-Dimensional Electrical Modeling of Axial p-i-n Junction InP Nanowire Array Solar Cells. In 2017 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD); 2017; pp 23−24. (394) Wu, D.; Tang, X.; Wang, K.; He, Z.; Li, X. An Efficient and Effective Design of InP Nanowires for Maximal Solar Energy Harvesting. Nanoscale Res. Lett. 2017, 12, 604. (395) Chen, Y.; Kivisaari, P.; Pistol, M.-E.; Anttu, N. Optimized Efficiency in InP Nanowire Solar Cells with Accurate 1D Analysis. Nanotechnology 2018, 29, 045401. (396) Bothra, S.; Tyagi, S.; Ghandhi, S. K.; Borrego, J. M. Surface Recombination Velocity and Lifetime in InP. Solid-State Electron. 1991, 34, 47−50. (397) Rosenwaks, Y.; Shapira, Y.; Huppert, D. Evidence for Low Intrinsic Surface-Recombination Velocity on p-Type InP. Phys. Rev. B: Condens. Matter Mater. Phys. 1991, 44, 13097−13100. (398) Wang, X.; Bhosale, J.; Moore, J.; Kapadia, R.; Bermel, P.; Javey, A.; Lundstrom, M. Photovoltaic Material Characterization With Steady State and Transient Photoluminescence. IEEE J. Photovolt. 2015, 5, 282−287. AS


Chemical Reviews

Review

(399) Münch, S.; Reitzenstein, S.; Borgström, M.; Thelander, C.; Samuelson, L.; Worschech, L.; Forchel, A. Time-Resolved Photoluminescence Investigations on HfO 2 -Capped InP Nanowires. Nanotechnology 2010, 21, 105711. (400) Dhaka, V.; Perros, A.; Naureen, S.; Shahid, N.; Jiang, H.; Kakko, J.-P.; Haggren, T.; Kauppinen, E.; Srinivasan, A.; Lipsanen, H. Protective Capping and Surface Passivation of III-V Nanowires by Atomic Layer Deposition. AIP Adv. 2016, 6, 015016. (401) Sautreuil, B.; Viktorovitch, P.; Blanchet, R. Evidence for Interfacial Defects in Metal-insulator-InP Structures Induced by the Insulator Deposition. J. Appl. Phys. 1985, 57, 2322−2324. (402) Mallorquí, A. D.; Alarcón-Lladó, E.; Mundet, I. C.; Kiani, A.; Demaurex, B.; De Wolf, S.; Menzel, A.; Zacharias, M.; Fontcuberta i Morral, A. Field-Effect Passivation on Silicon Nanowire Solar Cells. Nano Res. 2015, 8, 673−681. (403) Oener, S. Z.; Cavalli, A.; Sun, H.; Haverkort, J. E. M.; Bakkers, E. P. A. M.; Garnett, E. C. Charge Carrier-Selective Contacts for Nanowire Solar Cells. Nat. Commun. 2018, 9, 3248. (404) Jain, V.; Nowzari, A.; Wallentin, J.; Borgström, M. T.; Messing, M. E.; Asoli, D.; Graczyk, M.; Witzigmann, B.; Capasso, F.; Samuelson, L.; et al. Study of Photocurrent Generation in InP Nanowire-Based P+-i-N+ Photodetectors. Nano Res. 2014, 7, 544− 552. (405) Li, Z.; Yang, I.; Li, L.; Gao, Q.; Chong, J. S.; Li, Z.; Lockrey, M. N.; Tan, H. H.; Jagadish, C.; Fu, L. Reducing Zn Diffusion in Single Axial Junction InP Nanowire Solar Cells for Improved Performance. Prog. Nat. Sci. 2018, 28, 178−182. (406) Zhang, J.; Chia, A. C. E.; LaPierre, R. R. Low Resistance Indium Tin Oxide Contact to N-GaAs Nanowires. Semicond. Sci. Technol. 2014, 29, 054002. (407) Mariani, G.; Zhou, Z.; Scofield, A.; Huffaker, D. L. DirectBandgap Epitaxial Core−Multishell Nanopillar Photovoltaics Featuring Subwavelength Optical Concentrators. Nano Lett. 2013, 13, 1632−1637. (408) Ghahfarokhi, O. M.; Anttu, N.; Samuelson, L.; Åberg, I. Performance of GaAs Nanowire Array Solar Cells for Varying Incidence Angles. IEEE J. Photovolt. 2016, 6, 1502−1508. (409) Mikulik, D.; Ricci, M.; Tutuncuoglu, G.; Matteini, F.; Vukajlovic, J.; Vulic, N.; Alarcon-Llado, E.; Fontcuberta i Morral, A. Conductive-Probe Atomic Force Microscopy as a Characterization Tool for Nanowire-Based Solar Cells. Nano Energy 2017, 41, 566− 572. (410) Tchoulfian, P.; Donatini, F.; Levy, F.; Dussaigne, A.; Ferret, P.; Pernot, J. Direct Imaging of p−n Junction in Core−Shell GaN Wires. Nano Lett. 2014, 14, 3491−3498. (411) Lavenus, P.; Messanvi, A.; Rigutti, L.; De Luna Bugallo, A.; Zhang, H.; Bayle, F.; Julien, F. H.; Eymery, J.; Durand, C.; Tchernycheva, M. Experimental and Theoretical Analysis of Transport Properties of Core−Shell Wire Light Emitting Diodes Probed by Electron Beam Induced Current Microscopy. Nanotechnology 2014, 25, 255201. (412) Darbandi, A.; McNeil, J. C.; Akhtari-Zavareh, A.; Watkins, S. P.; Kavanagh, K. L. Direct Measurement of the Electrical Abruptness of a Nanowire p−n Junction. Nano Lett. 2016, 16, 3982−3988. (413) Darbandi, A.; Watkins, S. P. Measurement of Minority Carrier Diffusion Lengths in GaAs Nanowires by a Nanoprobe Technique. J. Appl. Phys. 2016, 120, 014301. (414) Heurlin, M.; Wickert, P.; Fält, S.; Borgström, M. T.; Deppert, K.; Samuelson, L.; Magnusson, M. H. Axial InP Nanowire Tandem Junction Grown on a Silicon Substrate. Nano Lett. 2011, 11, 2028− 2031. (415) LaPierre, R. R. Theoretical Conversion Efficiency of a TwoJunction III-V Nanowire on Si Solar Cell. J. Appl. Phys. 2011, 110, 014310. (416) Dorodnyy, A.; Alarcon-Lladó, E.; Shklover, V.; Hafner, C.; Fontcuberta i Morral, A.; Leuthold, J. Efficient Multiterminal Spectrum Splitting via a Nanowire Array Solar Cell. ACS Photonics 2015, 2, 1284−1288.

(417) Tchernycheva, M.; Rigutti, L.; Jacopin, G.; de Luna Bugallo, A.; Lavenus, P.; Julien, F. H.; Timofeeva, M.; Bouravleuv, A. D.; Cirlin, G. E.; Dhaka, V.; Lipsanen, H.; Largeau, L. Photovoltaic Properties of GaAsP Core−Shell Nanowires on Si(001) Substrate. Nanotechnology 2012, 23, 265402. (418) Holm, J. V.; Jørgensen, H. I.; Krogstrup, P.; Nygård, J.; Liu, H.; Aagesen, M. Surface-Passivated GaAsP Single-Nanowire Solar Cells Exceeding 10% Efficiency Grown on Silicon. Nat. Commun. 2013, 4, 1498. (419) Vettori, M.; Piazza, V.; Cattoni, A.; Scaccabarozzi, A.; Patriarche, G.; Regreny, P.; Chauvin, N.; Botella, C.; Grenet, G.; Penuelas, J.; et al. Growth Optimization and Characterization of Regular Arrays of GaAs/AlGaAs Core/Shell Nanowires for Tandem Solar Cells on Silicon. Nanotechnology 2019, 30, 084005. (420) Darbandi, A.; Kavanagh, K. L.; Watkins, S. P. LithographyFree Fabrication of Core−Shell GaAs Nanowire Tunnel Diodes. Nano Lett. 2015, 15, 5408−5413. (421) Ferreyra, R. A.; Zhu, C.; Teke, A.; Morkoç, H. Group III Nitrides. In Springer Handbook of Electronic and Photonic Materials; Springer Handbooks; Kasap, S., Capper, P., Eds.; Springer International Publishing: Cham, 2017; pp 1−1. (422) Morkoç, H. Nitride Semiconductors and Devices; Springer Series in Materials Science; Springer-Verlag: Berlin, Heidelberg, 1999. (423) Fritze, S.; Dadgar, A.; Witte, H.; Bügler, M.; Rohrbeck, A.; Bläsing, J.; Hoffmann, A.; Krost, A. High Si and Ge N-Type Doping of GaN Doping - Limits and Impact on Stress. Appl. Phys. Lett. 2012, 100, 122104. (424) Defects in Advanced Electronic Materials and Novel Low Dimensional Structures; Elsevier, 2018. (425) Sugiyama, T.; Iida, D.; Yasuda, T.; Iwaya, M.; Takeuchi, T.; Kamiyama, S.; Akasaki, I. Extremely Low-Resistivity and HighCarrier-Concentration Si-Doped Al0.05Ga0.95N. Appl. Phys. Express 2013, 6, 121002. (426) Ajay, A.; Schörmann, J.; Jiménez-Rodriguez, M.; Lim, C. B.; Walther, F.; Rohnke, M.; Mouton, I.; Amichi, L.; Bougerol, C.; Den Hertog, M. I.; Eickhoff, M.; Monroy, E. Ge Doping of GaN beyond the Mott Transition. J. Phys. Appl. Phys. 2016, 49, 445301. (427) Feneberg, M.; Osterburg, S.; Lange, K.; Lidig, C.; Garke, B.; Goldhahn, R.; Richter, E.; Netzel, C.; Neumann, M. D.; Esser, N.; et al. Band Gap Renormalization and Burstein-Moss Effect in Siliconand Germanium-Doped Wurtzite GaN up to 1020 cm−3. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90, 075203. (428) Leroux, M.; Beaumont, B.; Grandjean, N.; Lorenzini, P.; Haffouz, S.; Vennéguès, P.; Massies, J.; Gibart, P. Luminescence and Reflectivity Studies of Undoped, n- and p-Doped GaN on (0001) Sapphire. Mater. Sci. Eng., B 1997, 50, 97−104. (429) Nenstiel, C.; Callsen, G.; Nippert, F.; Kure, T.; Schlichting, S.; Jankowski, N.; Hoffmann, M. P.; Dadgar, A.; Fritze, S.; Krost, A.; Wagner, M. R.; Hoffmann, A.; Bechstedt, F. Electronic Excitations Stabilized by a Degenerate Electron Gas in Semiconductors. Commun. Phys. 2018, 1, 38. (430) Monemar, B.; Paskov, P. P.; Pozina, G.; Hemmingsson, C.; Bergman, J. P.; Khromov, S.; Izyumskaya, V. N.; Avrutin, V.; Li, X.; Morkoç, H.; et al. Properties of the Main Mg-Related Acceptors in GaN from Optical and Structural Studies. J. Appl. Phys. 2014, 115, 053507. (431) Chen, L.; Skromme, B. J. Spectroscopic Characterization of Ion-Implanted GaN. MRS Online Proc. Libr. Arch. 2002, 743, L11.35. (432) Burnham, S. D.; Namkoong, G.; Look, D. C.; Clafin, B.; Doolittle, W. A. Reproducible Increased Mg Incorporation and Large Hole Concentration in GaN Using Metal Modulated Epitaxy. J. Appl. Phys. 2008, 104, 024902. (433) Nakamura, S.; Mukai, T.; Senoh, M.; Iwasa, N. Thermal Annealing Effects on P-Type Mg-Doped GaN Films. Jpn. J. Appl. Phys. 1992, 31, L139. (434) Vennéguès, P.; Benaissa, M.; Beaumont, B.; Feltin, E.; De Mierry, P.; Dalmasso, S.; Leroux, M.; Gibart, P. Pyramidal Defects in Metalorganic Vapor Phase Epitaxial Mg Doped GaN. Appl. Phys. Lett. 2000, 77, 880−882. AT


Chemical Reviews

Review

(435) Liliental-Weber, Z.; Benamara, M.; Swider, W.; Washburn, J.; Grzegory, I.; Porowski, S.; Lambert, D. J. H.; Eiting, C. J.; Dupuis, R. D. Mg-Doped GaN: Similar Defects in Bulk Crystals and Layers Grown on Al2O3 by Metal−Organic Chemical-Vapor Deposition. Appl. Phys. Lett. 1999, 75, 4159−4161. (436) Gordon, L.; Lyons, J. L.; Janotti, A.; Van de Walle, C. G. Hybrid Functional Calculations of DX Centers in AlN and GaN. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 89, 085204. (437) Son, N. T.; Bickermann, M.; Janzén, E. Shallow Donor and DX States of Si in AlN. Appl. Phys. Lett. 2011, 98, 092104. (438) Trinh, X. T.; Nilsson, D.; Ivanov, I. G.; Janzén, E.; Kakanakova-Georgieva, A.; Son, N. T. Stable and Metastable Si Negative-U Centers in AlGaN and AlN. Appl. Phys. Lett. 2014, 105, 162106. (439) Nilsson, D.; Trinh, X. T.; Janzén, E.; Son, N. T.; KakanakovaGeorgieva, A. On the Behavior of Silicon Donor in Conductive AlxGa1−xN (0.63 ≤ x ≤ 1). Phys. Status Solidi B 2015, 252, 1306− 1310. (440) III-Nitride Ultraviolet Emitters: Technology and Applications; Springer Series in Materials Science; Kneissl, M., Rass, J., Eds.; Springer: Cham, Heidelberg, New York, Dordrecht, London, 2016. (441) Hirayama, H. Recent Progress in AlGaN Deep-UV LEDs. In Light-Emitting DiodeAn Outlook On the Empirical Features and Its Recent Technological Advancements; Thirumalai, J., Ed.; InTech, 2018. (442) Liu, Y.-S.; Kao, T.-T.; Satter, M. M.; Lochner, Z.; Li, X.-H.; Shen, S.-C.; Yoder, P. D.; Detchprohm, T.; Dupuis, R. D.; Wei, Y.; et al. Optically Pumped Deep-Ultraviolet AlGaN Multi-QuantumWell Lasers Grown by Metalorganic Chemical Vapor Deposition. In Novel In-Plane Semiconductor Lasers XIII; International Society for Optics and Photonics, 2014; Vol. 9002, p 90020H. (443) Liu, Z.; Yi, X.; Yu, Z.; Yuan, G.; Liu, Y.; Wang, J.; Li, J.; Lu, N.; Ferguson, I.; Zhang, Y. Impurity Resonant States P-Type Doping in Wide-Band-Gap Nitrides. Sci. Rep. 2016, 6, 19537. (444) Simon, J.; Protasenko, V.; Lian, C.; Xing, H.; Jena, D. Polarization-Induced Hole Doping in Wide−Band-Gap Uniaxial Semiconductor Heterostructures. Science 2010, 327, 60−64. (445) Walukiewicz, W.; Ager, J. W., III; Yu, K. M.; Liliental-Weber, Z.; Wu, J.; Li, S. X.; Jones, R. E.; Denlinger, J. D. Structure and Electronic Properties of InN and In-Rich Group III-Nitride Alloys. J. Phys. Appl. Phys. 2006, 39, R83. (446) Belabbes, A.; de Carvalho, L. C.; Schleife, A.; Bechstedt, F. Cubic Inclusions in Hexagonal AlN, GaN, and InN: Electronic States. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 84, 125108. (447) Wang, X.; Che, S.-B.; Ishitani, Y.; Yoshikawa, A. Growth and Properties of Mg-Doped In-Polar InN Films. Appl. Phys. Lett. 2007, 90, 201913. (448) Khromov, S.; Persson, P. O. Å.; Wang, X.; Yoshikawa, A.; Monemar, B.; Rosen, J.; Janzén, E.; Darakchieva, V. Correlation between Switching to N-Type Conductivity and Structural Defects in Highly Mg-Doped InN. Appl. Phys. Lett. 2015, 106, 232102. (449) Wang, G. T.; Talin, A. A.; Werder, D. J.; Creighton, J. R.; Lai, E.; Anderson, R. J.; Arslan, I. Highly Aligned, Template-Free Growth and Characterization of Vertical GaN Nanowires on Sapphire by Metal−Organic Chemical Vapour Deposition. Nanotechnology 2006, 17, 5773−5780. (450) Qian, F.; Li, Y.; Gradečak, S.; Park, H.-G.; Dong, Y.; Ding, Y.; Wang, Z. L.; Lieber, C. M. Multi-Quantum-Well Nanowire Heterostructures for Wavelength-Controlled Lasers. Nat. Mater. 2008, 7, 701−706. (451) Kuykendall, T. R.; Altoe, M. V. P.; Ogletree, D. F.; Aloni, S. Catalyst-Directed Crystallographic Orientation Control of GaN Nanowire Growth. Nano Lett. 2014, 14, 6767−6773. (452) Kuykendall, T.; Pauzauskie, P. J.; Zhang, Y.; Goldberger, J.; Sirbuly, D.; Denlinger, J.; Yang, P. Crystallographic Alignment of High-Density Gallium Nitride Nanowire Arrays. Nat. Mater. 2004, 3, 524−528. (453) Huang, C.-T.; Song, J.; Lee, W.-F.; Ding, Y.; Gao, Z.; Hao, Y.; Chen, L.-J.; Wang, Z. L. GaN Nanowire Arrays for High-Output Nanogenerators. J. Am. Chem. Soc. 2010, 132, 4766−4771.

(454) Qian, F.; Li, Y.; Gradečak, S.; Wang, D.; Barrelet, C. J.; Lieber, C. M. Gallium Nitride-Based Nanowire Radial Heterostructures for Nanophotonics. Nano Lett. 2004, 4, 1975−1979. (455) Ra, Y.-H.; Navamathavan, R.; Park, J.-H.; Lee, C.-R. HighQuality Uniaxial In x Ga 1− x N/GaN Multiple Quantum Well (MQW) Nanowires (NWs) on Si(111) Grown by Metal-Organic Chemical Vapor Deposition (MOCVD) and Light-Emitting Diode (LED) Fabrication. ACS Appl. Mater. Interfaces 2013, 5, 2111−2117. (456) Ra, Y.-H.; Navamathavan, R.; Park, J.-H.; Lee, C.-R. Coaxial In x Ga 1− x N/GaN Multiple Quantum Well Nanowire Arrays on Si(111) Substrate for High-Performance Light-Emitting Diodes. Nano Lett. 2013, 13, 3506−3516. (457) Gamalski, A. D.; Tersoff, J.; Stach, E. A. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires. Nano Lett. 2016, 16, 2283−2288. (458) Northrup, J. E.; Neugebauer, J. Strong Affinity of Hydrogen for the GaN(000−1) Surface: Implications for Molecular Beam Epitaxy and Metalorganic Chemical Vapor Deposition. Appl. Phys. Lett. 2004, 85, 3429−3431. (459) Jindal, V.; Shahedipour-Sandvik, F. Theoretical Prediction of GaN Nanostructure Equilibrium and Nonequilibrium Shapes. J. Appl. Phys. 2009, 106, 083115. (460) Ra, Y.-H.; Navamathavan, R.; Yoo, H.-I.; Lee, C.-R. Single Nanowire Light-Emitting Diodes Using Uniaxial and Coaxial InGaN/ GaN Multiple Quantum Wells Synthesized by Metalorganic Chemical Vapor Deposition. Nano Lett. 2014, 14, 1537−1545. (461) Consonni, V.; Knelangen, M.; Geelhaar, L.; Trampert, A.; Riechert, H. Nucleation Mechanisms of Epitaxial GaN Nanowires: Origin of Their Self-Induced Formation and Initial Radius. Phys. Rev. B 2010, 81, 085310. (462) Guo, W.; Zhang, M.; Banerjee, A.; Bhattacharya, P. CatalystFree InGaN/GaN Nanowire Light Emitting Diodes Grown on (001) Silicon by Molecular Beam Epitaxy. Nano Lett. 2010, 10, 3355−3359. (463) Jahangir, S.; Mandl, M.; Strassburg, M.; Bhattacharya, P. Molecular Beam Epitaxial Growth and Optical Properties of RedEmitting (λ = 650 Nm) InGaN/GaN Disks-in-Nanowires on Silicon. Appl. Phys. Lett. 2013, 102, 071101. (464) Sun, H.; Priante, D.; Min, J.-W.; Subedi, R. C.; Shakfa, M. K.; Ren, Z.; Li, K.-H.; Lin, R.; Zhao, C.; Ng, T. K.; et al. Graded-Index Separate Confinement Heterostructure AlGaN Nanowires: Toward Ultraviolet Laser Diodes Implementation. ACS Photonics 2018, 5, 3305−3314. (465) Chang, Y.-L.; Wang, J. L.; Li, F.; Mi, Z. High Efficiency Green, Yellow, and Amber Emission from InGaN/GaN Dot-in-a-Wire Heterostructures on Si(111). Appl. Phys. Lett. 2010, 96, 013106. (466) Lin, H.-W.; Lu, Y.-J.; Chen, H.-Y.; Lee, H.-M.; Gwo, S. InGaN/GaN Nanorod Array White Light-Emitting Diode. Appl. Phys. Lett. 2010, 97, 073101. (467) Goodman, K. D.; Protasenko, V. V.; Verma, J.; Kosel, T. H.; Xing, H. G.; Jena, D. Green Luminescence of InGaN Nanowires Grown on Silicon Substrates by Molecular Beam Epitaxy. J. Appl. Phys. 2011, 109, 084336. (468) Fernández-Garrido, S.; Kaganer, V. M.; Sabelfeld, K. K.; Gotschke, T.; Grandal, J.; Calleja, E.; Geelhaar, L.; Brandt, O. SelfRegulated Radius of Spontaneously Formed GaN Nanowires in Molecular Beam Epitaxy. Nano Lett. 2013, 13, 3274−3280. (469) Zettler, J. K.; Hauswald, C.; Corfdir, P.; Musolino, M.; Geelhaar, L.; Riechert, H.; Brandt, O.; Fernández-Garrido, S. HighTemperature Growth of GaN Nanowires by Molecular Beam Epitaxy: Toward the Material Quality of Bulk GaN. Cryst. Growth Des. 2015, 15, 4104−4109. (470) Deshpande, S.; Frost, T.; Yan, L.; Jahangir, S.; Hazari, A.; Liu, X.; Mirecki-Millunchick, J.; Mi, Z.; Bhattacharya, P. Formation and Nature of InGaN Quantum Dots in GaN Nanowires. Nano Lett. 2015, 15, 1647−1653. (471) Kumaresan, V.; Largeau, L.; Madouri, A.; Glas, F.; Zhang, H.; Oehler, F.; Cavanna, A.; Babichev, A.; Travers, L.; Gogneau, N.; et al. Epitaxy of GaN Nanowires on Graphene. Nano Lett. 2016, 16, 4895− 4902. AU


Chemical Reviews

Review

Nanowire Superlattices by Germanium Doping. Appl. Phys. Lett. 2014, 104, 102104. (488) Das, A.; Heo, J.; Jankowski, M.; Guo, W.; Zhang, L.; Deng, H.; Bhattacharya, P. Room Temperature Ultralow Threshold GaN Nanowire Polariton Laser. Phys. Rev. Lett. 2011, 107, 066405. (489) Heo, J.; Guo, W.; Bhattacharya, P. Monolithic Single GaN Nanowire Laser with Photonic Crystal Microcavity on Silicon. Appl. Phys. Lett. 2011, 98, 021110. (490) Woo, S. Y.; Gauquelin, N.; Nguyen, H. P. T.; Mi, Z.; Botton, G. A. Interplay of Strain and Indium Incorporation in InGaN/GaN Dot-in-a-Wire Nanostructures by Scanning Transmission Electron Microscopy. Nanotechnology 2015, 26, 344002. (491) Kioseoglou, J.; Pavloudis, Th.; Kehagias, Th.; Komninou, Ph.; Karakostas, Th.; Latham, C. D.; Rayson, M. J.; Briddon, P. R.; Eickhoff, M. Structural and Electronic Properties of GaN Nanowires with Embedded In x Ga 1− x N Nanodisks. J. Appl. Phys. 2015, 118, 034301. (492) Guo, W.; Zhang, M.; Bhattacharya, P.; Heo, J. Auger Recombination in III-Nitride Nanowires and Its Effect on Nanowire Light-Emitting Diode Characteristics. Nano Lett. 2011, 11, 1434− 1438. (493) Sadaf, S. M.; Ra, Y.-H.; Nguyen, H. P. T.; Djavid, M.; Mi, Z. Alternating-Current InGaN/GaN Tunnel Junction Nanowire WhiteLight Emitting Diodes. Nano Lett. 2015, 15, 6696−6701. (494) Nguyen, H. P. T.; Zhang, S.; Connie, A. T.; Kibria, M. G.; Wang, Q.; Shih, I.; Mi, Z. Breaking the Carrier Injection Bottleneck of Phosphor-Free Nanowire White Light-Emitting Diodes. Nano Lett. 2013, 13, 5437−5442. (495) Mitchell, B.; Dierolf, V.; Gregorkiewicz, T.; Fujiwara, Y. Perspective: Toward Efficient GaN-Based Red Light Emitting Diodes Using Europium Doping. J. Appl. Phys. 2018, 123, 160901. (496) Sukegawa, A.; Sekiguchi, H.; Matsuzaki, R.; Yamane, K.; Okada, H.; Kishino, K.; Wakahara, A. Self-Organized Eu-Doped GaN Nanocolumn Light-Emitting Diode Grown by RF-Molecular-Beam Epitaxy. Phys. Status Solidi A 2018, 216, 1800501. (497) Zhao, S.; Woo, S. Y.; Sadaf, S. M.; Wu, Y.; Pofelski, A.; Laleyan, D. A.; Rashid, R. T.; Wang, Y.; Botton, G. A.; Mi, Z. Molecular Beam Epitaxy Growth of Al-Rich AlGaN Nanowires for Deep Ultraviolet Optoelectronics. APL Mater. 2016, 4, 086115. (498) Pierret, A.; Bougerol, C.; Murcia-Mascaros, S.; Cros, A.; Renevier, H.; Gayral, B.; Daudin, B. Growth, Structural and Optical Properties of AlGaN Nanowires in the Whole Composition Range. Nanotechnology 2013, 24, 115704. (499) Zhao, S.; Mi, Z. AlGaN Nanowires: Path to Electrically Injected Semiconductor Deep Ultraviolet Lasers. IEEE J. Quantum Electron. 2018, 54, 1−9. (500) Mi, Z.; Zhao, S.; Woo, S. Y.; Bugnet, M.; Djavid, M.; Liu, X.; Kang, J.; Kong, X.; Ji, W.; Guo, H.; et al. Molecular Beam Epitaxial Growth and Characterization of Al(Ga)N Nanowire Deep Ultraviolet Light Emitting Diodes and Lasers. J. Phys. D: Appl. Phys. 2016, 49, 364006. (501) Tran, N. H.; Le, B. H.; Zhao, S.; Mi, Z. On the Mechanism of Highly Efficient P-Type Conduction of Mg-Doped Ultra-WideBandgap AlN Nanostructures. Appl. Phys. Lett. 2017, 110, 032102. (502) Zhao, S.; Connie, A. T.; Dastjerdi, M. H. T.; Kong, X. H.; Wang, Q.; Djavid, M.; Sadaf, S.; Liu, X. D.; Shih, I.; Guo, H.; Mi, Z. Aluminum Nitride Nanowire Light Emitting Diodes: Breaking the Fundamental Bottleneck of Deep Ultraviolet Light Sources. Sci. Rep. 2015, 5, 8332. (503) Connie, A. T.; Zhao, S.; Sadaf, S. Md.; Shih, I.; Mi, Z.; Du, X.; Lin, J.; Jiang, H. Optical and Electrical Properties of Mg-Doped AlN Nanowires Grown by Molecular Beam Epitaxy. Appl. Phys. Lett. 2015, 106, 213105. (504) Zhao, S.; Djavid, M.; Mi, Z. Surface Emitting, High Efficiency Near-Vacuum Ultraviolet Light Source with Aluminum Nitride Nanowires Monolithically Grown on Silicon. Nano Lett. 2015, 15, 7006−7009. (505) Li, K. H.; Liu, X.; Wang, Q.; Zhao, S.; Mi, Z. UltralowThreshold Electrically Injected AlGaN Nanowire Ultraviolet Lasers

(472) Fernández-Garrido, S.; Ramsteiner, M.; Gao, G.; Galves, L. A.; Sharma, B.; Corfdir, P.; Calabrese, G.; de Souza Schiaber, Z.; Pfüller, C.; Trampert, A.; et al. Molecular Beam Epitaxy of GaN Nanowires on Epitaxial Graphene. Nano Lett. 2017, 17, 5213−5221. (473) Liudi Mulyo, A.; Rajpalke, M. K.; Kuroe, H.; Vullum, P.-E.; Weman, H.; Fimland, B.-O.; Kishino, K. Vertical GaN Nanocolumns Grown on Graphene Intermediated with a Thin AlN Buffer Layer. Nanotechnology 2019, 30, 015604. (474) Schuster, F.; Weiszer, S.; Hetzl, M.; Winnerl, A.; Garrido, J. A.; Stutzmann, M. Influence of Substrate Material, Orientation, and Surface Termination on GaN Nanowire Growth. J. Appl. Phys. 2014, 116, 054301. (475) Wölz, M.; Hauswald, C.; Flissikowski, T.; Gotschke, T.; Fernández-Garrido, S.; Brandt, O.; Grahn, H. T.; Geelhaar, L.; Riechert, H. Epitaxial Growth of GaN Nanowires with High Structural Perfection on a Metallic TiN Film. Nano Lett. 2015, 15, 3743−3747. (476) Calabrese, G.; Corfdir, P.; Gao, G.; Pfüller, C.; Trampert, A.; Brandt, O.; Geelhaar, L.; Fernández-Garrido, S. Molecular Beam Epitaxy of Single Crystalline GaN Nanowires on a Flexible Ti Foil. Appl. Phys. Lett. 2016, 108, 202101. (477) Zhao, C.; Ng, T. K.; Tseng, C.-C.; Li, J.; Shi, Y.; Wei, N.; Zhang, D.; Consiglio, G. B.; Prabaswara, A.; Alhamoud, A. A.; et al. InGaN/GaN Nanowires Epitaxy on Large-Area MoS 2 for HighPerformance Light-Emitters. RSC Adv. 2017, 7, 26665−26672. (478) Zhao, C.; Ng, T. K.; ElAfandy, R. T.; Prabaswara, A.; Consiglio, G. B.; Ajia, I. A.; Roqan, I. S.; Janjua, B.; Shen, C.; Eid, J.; et al. Droop-Free, Reliable, and High-Power InGaN/GaN Nanowire Light-Emitting Diodes for Monolithic Metal-Optoelectronics. Nano Lett. 2016, 16, 4616−4623. (479) Sarwar, A. G.; Carnevale, S. D.; Yang, F.; Kent, T. F.; Jamison, J. J.; McComb, D. W.; Myers, R. C. Semiconductor Nanowire LightEmitting Diodes Grown on Metal: A Direction Toward Large-Scale Fabrication of Nanowire Devices. Small 2015, 11, 5402−5408. (480) Auzelle, T.; Haas, B.; Minj, A.; Bougerol, C.; Rouvière, J.-L.; Cros, A.; Colchero, J.; Daudin, B. The Influence of AlN Buffer over the Polarity and the Nucleation of Self-Organized GaN Nanowires. J. Appl. Phys. 2015, 117, 245303. (481) Hestroffer, K.; Daudin, B. A RHEED Investigation of SelfAssembled GaN Nanowire Nucleation Dynamics on Bare Si and on Si Covered with a Thin AlN Buffer Layer: A RHEED Investigation of Self-Assembled GaN Nanowire Nucleation Dynamics on Bare Si and on Si Covered with a Thin AlN Buffer Layer. Phys. Status Solidi RRL 2013, 7, 835−839. (482) Sobanska, M.; Klosek, K.; Borysiuk, J.; Kret, S.; Tchutchulasvili, G.; Gieraltowska, S.; Zytkiewicz, Z. R. Enhanced Catalyst-Free Nucleation of GaN Nanowires on Amorphous Al 2 O 3 by Plasma-Assisted Molecular Beam Epitaxy. J. Appl. Phys. 2014, 115, 043517. (483) Sobanska, M.; Korona, K. P.; Zytkiewicz, Z. R.; Klosek, K.; Tchutchulashvili, G. Kinetics of Self-Induced Nucleation and Optical Properties of GaN Nanowires Grown by Plasma-Assisted Molecular Beam Epitaxy on Amorphous Al x O y. J. Appl. Phys. 2015, 118, 184303. (484) Siladie, A.-M.; Amichi, L.; Mollard, N.; Mouton, I.; Bonef, B.; Bougerol, C.; Grenier, A.; Robin, E.; Jouneau, P.-H.; Garro, N.; et al. Dopant Radial Inhomogeneity in Mg-Doped GaN Nanowires. Nanotechnology 2018, 29, 255706. (485) Fang, Z.; Robin, E.; Rozas-Jiménez, E.; Cros, A.; Donatini, F.; Mollard, N.; Pernot, J.; Daudin, B. Si Donor Incorporation in GaN Nanowires. Nano Lett. 2015, 15, 6794−6801. (486) Schörmann, J.; Hille, P.; Schäfer, M.; Müßener, J.; Becker, P.; Klar, P. J.; Kleine-Boymann, M.; Rohnke, M.; de la Mata, M.; Arbiol, J.; et al. Germanium Doping of Self-Assembled GaN Nanowires Grown by Plasma-Assisted Molecular Beam Epitaxy. J. Appl. Phys. 2013, 114, 103505. (487) Hille, P.; Müßener, J.; Becker, P.; de la Mata, M.; Rosemann, N.; Magén, C.; Arbiol, J.; Teubert, J.; Chatterjee, S.; Schörmann, J.; et al. Screening of the Quantum-Confined Stark Effect in AlN/GaN AV


Chemical Reviews

Review

on Si Operating at Low Temperature. Nat. Nanotechnol. 2015, 10, 140−144. (506) Zhao, S.; Liu, X.; Woo, S. Y.; Kang, J.; Botton, G. A.; Mi, Z. An Electrically Injected AlGaN Nanowire Laser Operating in the Ultraviolet-C Band. Appl. Phys. Lett. 2015, 107, 043101. (507) Zhao, S.; Liu, X.; Wu, Y.; Mi, Z. An Electrically Pumped 239 Nm AlGaN Nanowire Laser Operating at Room Temperature. Appl. Phys. Lett. 2016, 109, 191106. (508) Zhao, S.; Mi, Z. Recent Advances on P-Type III-Nitride Nanowires by Molecular Beam Epitaxy. Crystals 2017, 7, 268. (509) Sadaf, S. M.; Zhao, S.; Wu, Y.; Ra, Y.-H.; Liu, X.; Vanka, S.; Mi, Z. An AlGaN Core−Shell Tunnel Junction Nanowire LightEmitting Diode Operating in the Ultraviolet-C Band. Nano Lett. 2017, 17, 1212−1218. (510) Ajay, A.; Lim, C. B.; Browne, D. A.; Polaczyński, J.; BelletAmalric, E.; Bleuse, J.; den Hertog, M. I.; Monroy, E. Effect of Doping on the Intersubband Absorption in Si- and Ge-Doped GaN/AlN Heterostructures. Nanotechnology 2017, 28, 405204. (511) Ajay, A.; Blasco, R.; Polaczyński, J.; Spies, M.; Den Hertog, M. I.; Monroy, E. Intersubband Absorption in GaN Nanowire Heterostructures at Mid-Infrared Wavelengths. Nanotechnology 2018, 29, 385201. (512) Beeler, M.; Hille, P.; Schörmann, J.; Teubert, J.; de la Mata, M.; Arbiol, J.; Eickhoff, M.; Monroy, E. Intraband Absorption in SelfAssembled Ge-Doped GaN/AlN Nanowire Heterostructures. Nano Lett. 2014, 14, 1665−1673. (513) Zhao, S.; Salehzadeh, O.; Alagha, S.; Kavanagh, K. L.; Watkins, S. P.; Mi, Z. Probing the Electrical Transport Properties of Intrinsic InN Nanowires. Appl. Phys. Lett. 2013, 102, 073102. (514) Zhao, S.; Fathololoumi, S.; Bevan, K. H.; Liu, D. P.; Kibria, M. G.; Li, Q.; Wang, G. T.; Guo, H.; Mi, Z. Tuning the Surface Charge Properties of Epitaxial InN Nanowires. Nano Lett. 2012, 12, 2877− 2882. (515) Zhao, S.; Le, B. H.; Liu, D. P.; Liu, X. D.; Kibria, M. G.; Szkopek, T.; Guo, H.; Mi, Z. P-Type InN Nanowires. Nano Lett. 2013, 13, 5509−5513. (516) Heilmann, M.; Munshi, A. M.; Sarau, G.; Göbelt, M.; Tessarek, C.; Fauske, V. T.; van Helvoort, A. T. J.; Yang, J.; Latzel, M.; Hoffmann, B.; et al. Vertically Oriented Growth of GaN Nanorods on Si Using Graphene as an Atomically Thin Buffer Layer. Nano Lett. 2016, 16, 3524−3532. (517) Koester, R.; Hwang, J. S.; Durand, C.; Le Si Dang, D.; Eymery, J. Self-Assembled Growth of Catalyst-Free GaN Wires by Metal− Organic Vapour Phase Epitaxy. Nanotechnology 2010, 21, 015602. (518) Chen, X. J.; Gayral, B.; Sam-Giao, D.; Bougerol, C.; Durand, C.; Eymery, J. Catalyst-Free Growth of High-Optical Quality GaN Nanowires by Metal-Organic Vapor Phase Epitaxy. Appl. Phys. Lett. 2011, 99, 251910. (519) Tessarek, C.; Heilmann, M.; Butzen, E.; Haab, A.; Hardtdegen, H.; Dieker, C.; Spiecker, E.; Christiansen, S. The Role of Si during the Growth of GaN Micro- and Nanorods. Cryst. Growth Des. 2014, 14, 1486−1492. (520) Wang, X.; Hartmann, J.; Mandl, M.; Sadat Mohajerani, M.; Wehmann, H.-H.; Strassburg, M.; Waag, A. Growth Kinetics and Mass Transport Mechanisms of GaN Columns by Selective Area Metal Organic Vapor Phase Epitaxy. J. Appl. Phys. 2014, 115, 163104. (521) Chen, X. J.; Perillat-Merceroz, G.; Sam-Giao, D.; Durand, C.; Eymery, J. Homoepitaxial Growth of Catalyst-Free GaN Wires on NPolar Substrates. Appl. Phys. Lett. 2010, 97, 151909. (522) Kim, H.-M.; Kim, D. S.; Park, Y. S.; Kim, D. Y.; Kang, T. W.; Chung, K. S. Growth of GaN Nanorods by a Hydride Vapor Phase Epitaxy Method. Adv. Mater. 2002, 14, 991−993. (523) Kim, H.-M.; Cho, Y.-H.; Lee, H.; Kim, S. I.; Ryu, S. R.; Kim, D. Y.; Kang, T. W.; Chung, K. S. High-Brightness Light Emitting Diodes Using Dislocation-Free Indium Gallium Nitride/Gallium Nitride Multiquantum-Well Nanorod Arrays. Nano Lett. 2004, 4, 1059−1062.

(524) Kuykendall, T.; Ulrich, P.; Aloni, S.; Yang, P. Complete Composition Tunability of InGaN Nanowires Using a Combinatorial Approach. Nat. Mater. 2007, 6, 951−956. (525) Zeghouane, M.; Avit, G.; André, Y.; Bougerol, C.; Robin, Y.; Ferret, P.; Castelluci, D.; Gil, E.; Dubrovskii, V. G.; Amano, H.; et al. Compositional Control of Homogeneous InGaN Nanowires with the In Content up to 90%. Nanotechnology 2019, 30, 044001. (526) Beaumont, B.; Vennéguès, P.; Gibart, P. Epitaxial Lateral Overgrowth of GaN. Phys. Status Solidi B 2001, 227, 1−43. (527) Kishino, K.; Sekiguchi, H.; Kikuchi, A. Improved Ti-Mask Selective-Area Growth (SAG) by Rf-Plasma-Assisted Molecular Beam Epitaxy Demonstrating Extremely Uniform GaN Nanocolumn Arrays. J. Cryst. Growth 2009, 311, 2063−2068. (528) Kishino, K.; Ishizawa, S. Selective-Area Growth of GaN Nanocolumns on Si(111) Substrates for Application to Nanocolumn Emitters with Systematic Analysis of Dislocation Filtering Effect of Nanocolumns. Nanotechnology 2015, 26, 225602. (529) Sekiguchi, H.; Kishino, K.; Kikuchi, A. Emission Color Control from Blue to Red with Nanocolumn Diameter of InGaN/ GaN Nanocolumn Arrays Grown on Same Substrate. Appl. Phys. Lett. 2010, 96, 231104. (530) Sekiguchi, H.; Kishino, K.; Kikuchi, A. Ti-Mask Selective-Area Growth of GaN by RF-Plasma-Assisted Molecular-Beam Epitaxy for Fabricating Regularly Arranged InGaN/GaN Nanocolumns. Appl. Phys. Express 2008, 1, 124002. (531) Gotschke, T.; Schumann, T.; Limbach, F.; Stoica, T.; Calarco, R. Influence of the Adatom Diffusion on Selective Growth of GaN Nanowire Regular Arrays. Appl. Phys. Lett. 2011, 98, 103102. (532) Brubaker, M. D.; Duff, S. M.; Harvey, T. E.; Blanchard, P. T.; Roshko, A.; Sanders, A. W.; Sanford, N. A.; Bertness, K. A. PolarityControlled GaN/AlN Nucleation Layers for Selective-Area Growth of GaN Nanowire Arrays on Si(111) Substrates by Molecular Beam Epitaxy. Cryst. Growth Des. 2016, 16, 596−604. (533) Yamano, K.; Kishino, K. Selective Area Growth of InGaNBased Nanocolumn LED Crystals on AlN/Si Substrates Useful for Integrated μ-LED Fabrication. Appl. Phys. Lett. 2018, 112, 091105. (534) Liu, X.; Le, B. H.; Woo, S. Y.; Zhao, S.; Pofelski, A.; Botton, G. A.; Mi, Z. Selective Area Epitaxy of AlGaN Nanowire Arrays across Nearly the Entire Compositional Range for Deep Ultraviolet Photonics. Opt. Express 2017, 25, 30494. (535) Li, S. F.; Fuendling, S.; Wang, X.; Merzsch, S.; Al-Suleiman, M. A. M.; Wei, J. D.; Wehmann, H.-H.; Waag, A.; Bergbauer, W.; Strassburg, M. Polarity and Its Influence on Growth Mechanism during MOVPE Growth of GaN Sub-Micrometer Rods. Cryst. Growth Des. 2011, 11, 1573−1577. (536) Feenstra, R. M.; Dong, Y.; Lee, C. D.; Northrup, J. E. Recent Developments in Surface Studies of GaN and AlN. J. Vac. Sci. Technol., B: Microelectron. Process. Phenom. 2005, 23, 1174. (537) Hersee, S. D.; Sun, X.; Wang, X. The Controlled Growth of GaN Nanowires. Nano Lett. 2006, 6, 1808−1811. (538) Lin, Y.-T.; Yeh, T.-W.; Daniel Dapkus, P. Mechanism of Selective Area Growth of GaN Nanorods by Pulsed Mode Metalorganic Chemical Vapor Deposition. Nanotechnology 2012, 23, 465601. (539) Jung, B. O.; Bae, S.-Y.; Kato, Y.; Imura, M.; Lee, D.-S.; Honda, Y.; Amano, H. Morphology Development of GaN Nanowires Using a Pulsed-Mode MOCVD Growth Technique. CrystEngComm 2014, 16, 2273−2282. (540) Zhang, X.; Yang, S.; Tu, C.-G.; Kiang, Y.-W.; Yang, C. C. Growth Model of a GaN Nanorod with the Pulsed-Growth Technique of Metalorganic Chemical Vapor Deposition. Cryst. Growth Des. 2018, 18, 3767−3773. (541) Tu, C.-G.; Su, C.-Y.; Liao, C.-H.; Hsieh, C.; Yao, Y.-F.; Chen, H.-T.; Lin, C.-H.; Weng, C.-M.; Kiang, Y.-W.; Yang, C. C. Regularly Patterned Multi-Section GaN Nanorod Arrays Grown with a Pulsed Growth Technique. Nanotechnology 2016, 27, 025303. (542) Seifert, W.; Asoli, D.; Bi, Z. Nitride Nanowires and Method of Producing Such. U.S. Patent US7829443B2, November 9, 2010. AW


Chemical Reviews

Review

(543) Choi, K.; Arita, M.; Arakawa, Y. Selective-Area Growth of Thin GaN Nanowires by MOCVD. J. Cryst. Growth 2012, 357, 58− 61. (544) Akiyama, T.; Ammi, D.; Nakamura, K.; Ito, T. Surface Reconstruction and Magnesium Incorporation on Semipolar GaN (1 1 ̅ 01) Surfaces. Phys. Rev. B 2010, 81, 245317. (545) Bae, S.-Y.; Jung, B. O.; Lekhal, K.; Kim, S. Y.; Lee, J. Y.; Lee, D.-S.; Deki, M.; Honda, Y.; Amano, H. Highly Elongated Vertical GaN Nanorod Arrays on Si Substrates with an AlN Seed Layer by Pulsed-Mode Metal−Organic Vapor Deposition. CrystEngComm 2016, 18, 1505−1514. (546) Bergbauer, W.; Strassburg, M.; Kölper, C.; Linder, N.; Roder, C.; Lähnemann, J.; Trampert, A.; Fündling, S.; Li, S. F.; Wehmann, H.-H.; et al. Continuous-Flux MOVPE Growth of PositionControlled N-Face GaN Nanorods and Embedded InGaN Quantum Wells. Nanotechnology 2010, 21, 305201. (547) Bi, Z.; Gustafsson, A.; Lenrick, F.; Lindgren, D.; Hultin, O.; Wallenberg, L. R.; Ohlsson, B. J.; Monemar, B.; Samuelson, L. High In-Content InGaN Nano-Pyramids: Tuning Crystal Homogeneity by Optimized Nucleation of GaN Seeds. J. Appl. Phys. 2018, 123, 025102. (548) Shioda, T.; Tomita, Y.; Sugiyama, M.; Shimogaki, Y.; Nakano, Y. Selective Area Metal−Organic Vapor Phase Epitaxy of Nitride Semiconductors for Multicolor Emission. IEEE J. Sel. Top. Quantum Electron. 2009, 15, 1053−1065. (549) Hersee, S. D.; Rishinaramangalam, A. K.; Fairchild, M. N.; Zhang, L.; Varangis, P. Threading Defect Elimination in GaN Nanowires. J. Mater. Res. 2011, 26, 2293−2298. (550) Aseev, P.; Gačević, Ž .; Torres-Pardo, A.; González-Calbet, J. M.; Calleja, E. Improving Optical Performance of GaN Nanowires Grown by Selective Area Growth Homoepitaxy: Influence of Substrate and Nanowire Dimensions. Appl. Phys. Lett. 2016, 108, 253109. (551) Coulon, P.-M.; Alloing, B.; Brändli, V.; Vennéguès, P.; Leroux, M.; Zúñiga-Pérez, J. Dislocation Filtering and Polarity in the Selective Area Growth of GaN Nanowires by Continuous-Flow Metal Organic Vapor Phase Epitaxy. Appl. Phys. Express 2016, 9, 015502. (552) Wang, X.; Li, S.; Mohajerani, M. S.; Ledig, J.; Wehmann, H.H.; Mandl, M.; Strassburg, M.; Steegmüller, U.; Jahn, U.; Lähnemann, J.; et al. Continuous-Flow MOVPE of Ga-Polar GaN Column Arrays and Core−Shell LED Structures. Cryst. Growth Des. 2013, 13, 3475− 3480. (553) Lin, Y.-T.; Yeh, T.-W.; Nakajima, Y.; Dapkus, P. D. CatalystFree GaN Nanorods Synthesized by Selective Area Growth. Adv. Funct. Mater. 2014, 24, 3162−3171. (554) Müller, M.; Veit, P.; Krause, F. F.; Schimpke, T.; Metzner, S.; Bertram, F.; Mehrtens, T.; Müller-Caspary, K.; Avramescu, A.; Strassburg, M.; et al. Nanoscopic Insights into InGaN/GaN Core− Shell Nanorods: Structure, Composition, and Luminescence. Nano Lett. 2016, 16, 5340−5346. (555) Schmidt, G.; Müller, M.; Veit, P.; Metzner, S.; Bertram, F.; Hartmann, J.; Zhou, H.; Wehmann, H.-H.; Waag, A.; Christen, J. Direct Imaging of Indium-Rich Triangular Nanoprisms Self-Organized Formed at the Edges of InGaN/GaN Core-Shell Nanorods. Sci. Rep. 2018, 8, 16026. (556) Mahaboob, I.; Hogan, K.; Novak, S. W.; Shahedipour-Sandvik, F.; Tompkins, R. P.; Lazarus, N. Influence of Mask Material on the Electrical Properties of Selective Area Epitaxy GaN Microstructures. J. Vac. Sci. Technol., B: Nanotechnol. Microelectron.: Mater., Process., Meas., Phenom. 2018, 36, 031203. (557) Li, S.; Waag, A. GaN Based Nanorods for Solid State Lighting. J. Appl. Phys. 2012, 111, 071101. (558) Sun, Q.; Kwon, S.-Y.; Ren, Z.; Han, J.; Onuma, T.; Chichibu, S. F.; Wang, S. Microstructural Evolution in M-Plane GaN Growth on m-Plane SiC. Appl. Phys. Lett. 2008, 92, 051112. (559) Yeh, T.-W.; Lin, Y.-T.; Stewart, L. S.; Dapkus, P. D.; Sarkissian, R.; O’Brien, J. D.; Ahn, B.; Nutt, S. R. InGaN/GaN Multiple Quantum Wells Grown on Nonpolar Facets of Vertical GaN Nanorod Arrays. Nano Lett. 2012, 12, 3257−3262.

(560) Tzou, A.-J.; Hsieh, D.-H.; Hong, K.-B.; Lin, D.-W.; Huang, J.K.; Chen, T.-P.; Kao, T.-S.; Chen, Y.-F.; Lu, T.-C.; Chen, C.-H.; et al. High-Efficiency InGaN/GaN Core−Shell Nanorod Light-Emitting Diodes With Low-Peak Blueshift and Efficiency Droop. IEEE Trans. Nanotechnol. 2017, 16, 355−358. (561) Zhang, H.; Jacopin, G.; Neplokh, V.; Largeau, L.; Julien, F. H.; Kryliouk, O.; Tchernycheva, M. Color Control of Nanowire InGaN/ GaN Light Emitting Diodes by Post-Growth Treatment. Nanotechnology 2015, 26, 465203. (562) Shahmohammadi, M.; Ganière, J.-D.; Zhang, H.; Ciechonski, R.; Vescovi, G.; Kryliouk, O.; Tchernycheva, M.; Jacopin, G. Excitonic Diffusion in InGaN/GaN Core−Shell Nanowires. Nano Lett. 2016, 16, 243−249. (563) Jung, B. O.; Bae, S.-Y.; Lee, S.; Kim, S. Y.; Lee, J. Y.; Honda, Y.; Amano, H. Emission Characteristics of InGaN/GaN Core-Shell Nanorods Embedded in a 3D Light-Emitting Diode. Nanoscale Res. Lett. 2016, 11, 215. (564) Tchernycheva, M.; Lavenus, P.; Zhang, H.; Babichev, A. V.; Jacopin, G.; Shahmohammadi, M.; Julien, F. H.; Ciechonski, R.; Vescovi, G.; Kryliouk, O. InGaN/GaN Core−Shell Single Nanowire Light Emitting Diodes with Graphene-Based P-Contact. Nano Lett. 2014, 14, 2456−2465. (565) Kapoor, A.; Guan, N.; Vallo, M.; Messanvi, A.; Mancini, L.; Gautier, E.; Bougerol, C.; Gayral, B.; Julien, F. H.; Vurpillot, F.; et al. Green Electroluminescence from Radial m -Plane InGaN Quantum Wells Grown on GaN Wire Sidewalls by Metal−Organic Vapor Phase Epitaxy. ACS Photonics 2018, 5, 4330−4337. (566) Griffiths, J. T.; Ren, C. X.; Coulon, P.-M.; Le Boulbar, E. D.; Bryce, C. G.; Girgel, I.; Howkins, A.; Boyd, I.; Martin, R. W.; Allsopp, D. W. E.; et al. Structural Impact on the Nanoscale Optical Properties of InGaN Core-Shell Nanorods. Appl. Phys. Lett. 2017, 110, 172105. (567) Jung, W.-Y.; Kwak, C.-M.; Seol, J.-B.; Park, J. K.; Park, C.-G.; Jeong, Y. K. Observation of Anisotropic Growth and Compositional Discontinuity in AlGaN Electron-Blocking Layers on GaN Microrods. Cryst. Growth Des. 2018, 18, 1593−1597. (568) Stankevič, T.; Dzhigaev, D.; Bi, Z.; Rose, M.; Shabalin, A.; Reinhardt, J.; Mikkelsen, A.; Samuelson, L.; Falkenberg, G.; Vartanyants, I. A.; et al. Strain Mapping in an InGaN/GaN Nanowire Using a Nano-Focused x-Ray Beam. Appl. Phys. Lett. 2015, 107, 103101. (569) Nami, M.; Stricklin, I. E.; DaVico, K. M.; Mishkat-Ul-Masabih, S.; Rishinaramangalam, A. K.; Brueck, S. R. J.; Brener, I.; Feezell, D. F. Carrier Dynamics and Electro-Optical Characterization of HighPerformance GaN/InGaN Core-Shell Nanowire Light-Emitting Diodes. Sci. Rep. 2018, 8, 501. (570) Kum, H.; Seong, H.-K.; Lim, W.; Chun, D.; Kim, Y.; Park, Y.; Yoo, G. Wafer-Scale Thermodynamically Stable GaN Nanorods via Two-Step Self-Limiting Epitaxy for Optoelectronic Applications. Sci. Rep. 2017, 7, 40893. (571) Behzadirad, M.; Nami, M.; Wostbrock, N.; Zamani Kouhpanji, M. R.; Feezell, D. F.; Brueck, S. R. J.; Busani, T. Scalable Top-Down Approach Tailored by Interferometric Lithography to Achieve LargeArea Single-Mode GaN Nanowire Laser Arrays on Sapphire Substrate. ACS Nano 2018, 12, 2373−2380. (572) Yu, F.; Rümmler, D.; Hartmann, J.; Caccamo, L.; Schimpke, T.; Strassburg, M.; Gad, A. E.; Bakin, A.; Wehmann, H.-H.; Witzigmann, B.; et al. Vertical Architecture for Enhancement Mode Power Transistors Based on GaN Nanowires. Appl. Phys. Lett. 2016, 108, 213503. (573) Li, C.; Wright, J. B.; Liu, S.; Lu, P.; Figiel, J. J.; Leung, B.; Chow, W. W.; Brener, I.; Koleske, D. D.; Luk, T.-S.; et al. Nonpolar InGaN/GaN Core−Shell Single Nanowire Lasers. Nano Lett. 2017, 17, 1049−1055. (574) Jiao, Q.; Chen, Z.; Feng, Y.; Li, S.; Jiang, S.; Li, J.; Chen, Y.; Yu, T.; Kang, X.; Shen, B.; Zhang, G. The Effects of Nanocavity and Photonic Crystal in InGaN/GaN Nanorod LED Arrays. Nanoscale Res. Lett. 2016, 11, 340. (575) Yu, F.; Yao, S.; Römer, F.; Witzigmann, B.; Schimpke, T.; Strassburg, M.; Bakin, A.; Schumacher, H. W.; Peiner, E.; Wasisto, H. AX


Chemical Reviews

Review

S.; et al. GaN Nanowire Arrays with Nonpolar Sidewalls for Vertically Integrated Field-Effect Transistors. Nanotechnology 2017, 28, 095206. (576) Li, C.; Liu, S.; Luk, T. S.; Figiel, J. J.; Brener, I.; Brueck, S. R. J.; Wang, G. T. Intrinsic Polarization Control in Rectangular GaN Nanowire Lasers. Nanoscale 2016, 8, 5682−5687. (577) Hugues, M.; Shields, P. A.; Sacconi, F.; Mexis, M.; Auf der Maur, M.; Cooke, M.; Dineen, M.; Di Carlo, A.; Allsopp, D. W. E.; Zúñiga-Pérez, J. Strain Evolution in GaN Nanowires: From FreeSurface Objects to Coalesced Templates. J. Appl. Phys. 2013, 114, 084307. (578) Le Boulbar, E. D.; Edwards, P. R.; Vajargah, S. H.; Griffiths, I.; Gîrgel, I.; Coulon, P.-M.; Cherns, D.; Martin, R. W.; Humphreys, C. J.; Bowen, C. R.; et al. Structural and Optical Emission Uniformity of m -Plane InGaN Single Quantum Wells in Core−Shell Nanorods. Cryst. Growth Des. 2016, 16, 1907−1916. (579) Riley, J. R.; Padalkar, S.; Li, Q.; Lu, P.; Koleske, D. D.; Wierer, J. J.; Wang, G. T.; Lauhon, L. J. Three-Dimensional Mapping of Quantum Wells in a GaN/InGaN Core−Shell Nanowire LightEmitting Diode Array. Nano Lett. 2013, 13, 4317−4325. (580) Yu, F.; Strempel, K.; Fatahilah, M. F.; Zhou, H.; Romer, F.; Bakin, A.; Witzigmann, B.; Schumacher, H. W.; Wasisto, H. S.; Waag, A. Normally Off Vertical 3-D GaN Nanowire MOSFETs With Inverted ${p}$ -GaN Channel. IEEE Trans. Electron Devices 2018, 65, 2439−2445. (581) Son, D.-H.; Jo, Y.-W.; Seo, J. H.; Won, C.-H.; Im, K.-S.; Lee, Y. S.; Jang, H. S.; Kim, D.-H.; Kang, I. M.; Lee, J.-H. Low Voltage Operation of GaN Vertical Nanowire MOSFET. Solid-State Electron. 2018, 145, 1−7. (582) Sabui, G.; Zubialevich, V. Z.; White, M.; Pampili, P.; Parbrook, P. J.; McLaren, M.; Arredondo-Arechavala, M.; Shen, Z. J. GaN Nanowire Schottky Barrier Diodes. IEEE Trans. Electron Devices 2017, 64, 2283−2290. (583) Palacios, T. Gallium Nitride and the New Computer Revolution. In International Workshop on Nitride Semiconductors; Kanazawa, Japan, 2018. (584) Sun, M.; Zhang, Y.; Gao, X.; Palacios, T. High-Performance GaN Vertical Fin Power Transistors on Bulk GaN Substrates. IEEE Electron Device Lett. 2017, 38, 509−512. (585) Chen, Q.; Yan, C.; Qu, Y. 1.55 μ m Emission from a Single IIINitride Top-down and Site-Controlled Nanowire Quantum Disk. Mater. Res. Express 2017, 4, 075002. (586) Higo, A.; Kiba, T.; Chen, S.; Chen, Y.; Tanikawa, T.; Thomas, C.; Lee, C. Y.; Lai, Y.-C.; Ozaki, T.; Takayama, J.; et al. Optical Study of Sub-10 Nm In 0.3 Ga 0.7 N Quantum Nanodisks in GaN Nanopillars. ACS Photonics 2017, 4, 1851−1857. (587) Wang, G. T.; Li, Q.; Wierer, J. J.; Koleske, D. D.; Figiel, J. J. Top-down Fabrication and Characterization of Axial and Radial IIINitride Nanowire LEDs: Fabrication and Characterization of Axial and Radial III-Nitride NW LEDs. Phys. Status Solidi A 2014, 211, 748−751. (588) Bai, J.; Wang, Q.; Wang, T. Greatly Enhanced Performance of InGaN/GaN Nanorod Light Emitting Diodes. Phys. Status Solidi A 2012, 209, 477−480. (589) Teng, C.-H.; Zhang, L.; Deng, H.; Ku, P.-C. Strain-Induced Red-Green-Blue Wavelength Tuning in InGaN Quantum Wells. Appl. Phys. Lett. 2016, 108, 071104. (590) Chung, K.; Sui, J.; Demory, B.; Teng, C.-H.; Ku, P.-C. Monolithic Integration of Individually Addressable Light-Emitting Diode Color Pixels. Appl. Phys. Lett. 2017, 110, 111103. (591) Chung, K.; Sui, J.; Demory, B.; Ku, P.-C. Color Mixing from Monolithically Integrated InGaN-Based Light-Emitting Diodes by Local Strain Engineering. Appl. Phys. Lett. 2017, 111, 041101. (592) Coulon, P.-M.; Kusch, G.; Fletcher, P.; Chausse, P.; Martin, R.; Shields, P. Hybrid Top-Down/Bottom-Up Fabrication of a Highly Uniform and Organized Faceted AlN Nanorod Scaffold. Materials 2018, 11, 1140. (593) Coulon, P.-M.; Kusch, G.; Martin, R. W.; Shields, P. A. Deep UV Emission from Highly Ordered AlGaN/AlN Core−Shell Nanorods. ACS Appl. Mater. Interfaces 2018, 10, 33441−33449.

(594) Dai, J.; Liu, B.; Zhuang, Z.; He, G.; Zhi, T.; Tao, T.; Xu, Q.; Li, Y.; Ge, H.; Xie, Z.; et al. Fabrication of AlGaN Nanorods with Different Al Compositions for Emission Enhancement in UV Range. Nanotechnology 2017, 28, 385205. (595) Atoms to Product: Aiming to Make Nanoscale Benefits LifeSized. https://www.darpa.mil/news-events/2014-08/22 (accessed Jun 24, 2019). (596) Samuelson, L. Fred Kavli Distinguished Lectureship in Nanoscience: NanowiresFrom Basic Materials Research to RealWorld Applications2014 MRS Fall MeetingMaterials Research Society, http://www.prolibraries.com/mrs/?select= session&sessionID=5736 (accessed Jan 30, 2019). (597) Bi, Z.; Lenrick, F.; Colvin, J.; Gustafsson, A.; Hultin, O.; Nowzari, A.; Lu, T.; Wallenberg, R.; Timm, R.; Mikkelsen, A.; Ohlsson, B. J.; Storm, K.; Monemar, B.; Samuelson, L. InGaN Platelets: Synthesis and Applications toward Green and Red LightEmitting Diodes. Nano Lett. 2019, 19, 2832−2839.

AY


Synthesis and Applications of IIIâV Nanowires | Chemical Reviews

Recommend Documents

Synthesis and Applications of IIIâV Nanowires | Chemical Reviews