High Performance Vertical Resonant Photo-Effect-Transistor with an

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High Performance Vertical Resonant PhotoEffect-Transistor with an All-Around OLEDGate for Ultra-Electromagnetic Stability Qikun Li,†,‡,⊥ Sheng Bi,†,‡,⊥ Kyeiwaa Asare-Yeboah,§ Jin Na,† Yun Liu,∥ Chengming Jiang,*,†,‡ and Jinhui Song*,†,‡ Downloaded via BUFFALO STATE on July 19, 2019 at 16:04:49 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

†

Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education, Dalian University of Technology, Dalian 116024, China ‡ Institute of Photoelectric Nanoscience and Nanotechnology, School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China § Department of Electrical and Computer Engineering, Penn State Behrend, Erie, Pennsylvania 16563, United States ∥ Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States S Supporting Information *

ABSTRACT: The utilization of three-dimensional (3D) structures in next-generation nanodevices has been attractive due to the exceptional features they offer. These 3D structures can reduce component space and improve device properties compared to thin-film electronic components. The type of transistor applied in 3D nanodevices is one of the most widely studied components due to its rich physics and ubiquitous application. In this paper, we report a complete functionalized component, a 3D vertical resonant photo-effect-transistor (VRPET), which is realized with the functionalized nanowire current channel, asymmetric ohmic/Schottky contacts, and an ultraviolet photogate with an organic light emission diode (OLED) excitation. To enhance the VRPET performance, analyses of the design and fabrication parameters were carried out, where the focus was specifically on the relationship between light resonance and absorption. The transistor developed here can operate up to a high voltage of 16.5 V and control currents up to 50 μA with an ultrastable performance under a strong electromagnetic interference. The VRPET with excellent properties is a step toward achieving integrated photoelectric devices and corresponding applications. KEYWORDS: photo-effect-transistor, OLED gate, nanowire channel, resonance, anti-electromagnetic interference he field-effect transistor (FET) is one of the most widely used semiconductor devices in the electronics industry. However, the increment in processing speed as inferred from Gordon Moore’s prediction on an integrated circuit scale is no longer applicable.1,2 Furthermore, the reduction in the size of FETs is reaching its limit due to physical and technical restrictions.3,4 Advancements of transistors such as GaN-based FETs and SiC-based FETs require incessant improvement in device performance.5,6 To help facilitate growth in the FET field, many designs and materials have been developed in recent years.7−11 For instance, the FinFET which is a quasi-three-dimensional silicon-based FET (Si-FET) with a fin (the source and drain) traversing beneath the gate has greatly enhanced the design of the FET.12 On the material front, two-dimensional (2D) materials used in transistors that take advantage of the significant atomic-thin layer properties to obtain potential

applicable FETs have been developed.10,13,14 To propel growth even further, derived devices of FETs, such as the quantum dots voltage transistor and semifloating gate transistor combined with the metal-oxide semiconductor (MOS) FET, have been created to exhibit fast speed and low-power performance.15,16 Almost all devices which are potential replacements or devices that promote FET-like digital logic devices apply an electric field that results from the gate terminal to govern carriers in the channel.17,18 Although some devices are claimed to possess special channel control methods, they are usually limited in practical large-scale logic circuits.19−21 Moreover, electromagnetic interference (EMI) is

T

© XXXX American Chemical Society

Received: May 28, 2019 Accepted: June 27, 2019 Published: June 27, 2019 A

DOI: 10.1021/acsnano.9b04163 ACS Nano XXXX, XXX, XXX−XXX

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Cite This: ACS Nano XXXX, XXX, XXX−XXX

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ACS Nano an adverse factor in electronic devices. It is considered to be an issue such as for large-scale integrations, radio frequency, and analog circuits, where electromagnetic waves usually work as coupling paths or unwanted antennas. Quantum effect and nanoconfinement of nanomaterials have been shown to enhance the performance of electronic semiconductor materials and devices.22,23 Nanowires (NWs), specifically, have proven to be favorable microstructures for various kinds of electronic devices.24,25 The outstanding properties of NWs, including absorption enhancement, high operation speed, lower dark-noise, and larger inner signal gain, provide excellent benefits for many notable applications.25,26 Owing to its relatively simple fabrication process, the zinc oxide (ZnO) NW, which possesses a wide band gap and an exceptional Schottky contact property, is the most promising candidate for electronic applications.25,27−30 Here we report a three-dimensional (3D) vertical resonant photo-effect-transistor (VRPET) with ZnO NW as the current conducting channel and an organic light-emitting diode (OLED) as the direct-control gate. The highly responsive photocurrent NW channel is manufactured using electronbeam-lithography (EBL) and further modified to have multiple functionalized layers to vastly improve the current response of the VRPET. Two nanoscale electrodes with different work functions connect to the NW at the top and the bottom to form ohmic and Schottky interconnects, respectively, for signal rectification. Additionally, as a complete functional innovative integrated circuit, the 3D structure of the VRPET employs an OLED which surrounds the ZnO NW as a photogate to directly control the channel conductivity by generating photoexcited electrons. The OLED function is in like manner as the gate electrode of an FET which uses the vertically developed electrical field at the gate terminal to control the amount of carriers in the channel. To guide the design of the VRPET, optical analyses were systematically performed to study the leaky mode resonances which affects the optical properties of NWs, such as the absorption efficiency and photoelectric response. To reveal the performance of the VRPET and its current control advantages, tests were carried out in a strong electromagnetic interference, where the experimental results proved that the photocontrol VRPET provides highly stable outputs compared to the classical SiFET. A 10 × 10 VRPET array device was fabricated to demonstrate a practical application of the VRPET for confirming its higher rectifying and current regulation capabilities. The superior performance that the VRPET exhibits compared to other nanoelectronic devices is reported here by highlighting their excellent optical-controlled properties obtained through the theoretical and experimental results.

Figure 1. Device structure and fundamental concept of the VRPET. (a) Schematic configuration of a VRPET cell. A ZnO NW channel surrounded by an OLED as the gate. (b) Circuit representation of the VRPET analog device. (c) Cross-sectional structure of the device with a tubular OLED as the gate and a vertical NW as the channel. The surface of the NW channel is modified by a functionalized layer, PDAD/PSS, and the OLED is composed of organic layers (PE/CBP/TAZ/BCP). Au point and circular electrodes at the top are the drain electrode for the NW channel and the anode for the OLED. A Schottky barrier is formed at the interface between the Au electrode and the top of the NW. Ca/Al electrode at the bottom of the structure is the cathode for OLED and the source electrode for the NW channel, respectively. (d) Top-view SEM image of a fabricated VRPET device. The inset shows a 45° tilted view of a ZnO NW after dry-etching.

This type of asymmetric structure provides an effective way to suppress dark current and improve the collection of photocarriers.31−33 The cross-sectional view of the VRPET is illustrated in Figure 1c. The VRPET consists of an intrinsic ZnO NW with a surface functionalized layer, a dielectric layer and an OLED on a silicon dioxide (SiO2) substrate. The source electrode (30 nm Ca/Al) is fabricated at bottom by EBL, thermal deposition, and lift-off techniques. The ZnO NW (about 300 nm in height and 50 nm in diameter) is sequentially fabricated by metal−organic chemical vapor deposition (MOCVD),27,34 EBL, and reactive ion etching (RIE) processes. The surface functionalized layer35 poly(diallyldimethylammonium chloride) (PDAD) and poly(styrenesulfonate) (PSS), and the dielectric layer poly(methyl methacrylate) (PMMA) are deposited by spin-coating. The OLED is formed via a thermal evaporation process. Au (30 nm) film is deposited on a pattern fabricated by EBL to accurately control the size and position of the top electrode. The gate and drain electrodes located on the top of both the OLED layer and ZnO NW are partially etched (details of the fabrication are depicted in Figure S1 in the Supporting Information). Figure 1d shows the top view of a scanning electron microscopy (SEM) image of the developed VRPET. The fabrication of each part of the VRPET accurately matched its generated design, and the size of the entire VRPET device

RESULTS AND DISCUSSION The experimental setup and the corresponding circuit representation of the VRPET are schematically shown in Figure 1a and b. A vertical ZnO NW sandwiched between the drain electrode at the top and source electrode at the bottom is enclosed by a tubular OLED. The illuminated portion of the OLED material is determined by the shape of the gate and source electrodes; a top annular electrode and a bottom circular metal electrode, respectively. The bottom Ca/Al electrode develops ohmic contacts for source electrode. On the contrary, the top Au electrode provides the junction for the drain electrode and creates a Schottky barrier at the surface of the ZnO NW (shown as the embedded barrier in Figure 1b).30 B


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Figure 2. (a) Band energy diagram of ZnO NW channel. (Left) In the dark, the functionalized layer captures free electrons in the conduction band which bends the band on NW surface. (Right) Under illumination, the functionalized layer creates electron hole pairs. The free electrons stay at conduction band, which reduces the degree of band bending, increasing the conductivity of the NW. (b) Energy band diagram of the ZnO NW and Au electrode as a Schottky barrier in the VRPET. (c) Electric potential diagram of the fabricated TAZ OLED as the excitation photogate for the VRPET. (d) Typical I−V curves of the ZnO NW channel with the Schottky barrier under different light intensities. (e) Absorption spectrum of the ZnO NW as a function of wavelength. The inset is the typical EL spectrum of the TAZ OLED as a function of wavelength, whose emission peak is 370 nm. This comparison confirms the suitable matching of the ZnO channel and the TAZ OLED gate. (f) Intensity spectra of the fabricated TAZ OLED as a function of applied voltage.

measured less than 1 μm. The inset of Figure 1d illustrates the ZnO NW with a height of 300 nm and diameter of 50 nm. To understand the properties of the VRPET, it was paramount to systematically study each functional section of the device. ZnO NW, the chosen VRPET channel material produces charges under the irradiation of ultraviolet light, and has a relatively high photoelectrical on/off ratio compared to other materials.13,26 The designed ZnO NW channel is functionalized by the molecular (PDAD and PSS) layer which is adsorbed on the surface of ZnO NW to capture free electrons that form a depletion region.35 This process helps the ZnO NWs increase their photoelectrical on/off ratios and response speed (as detailed in Figures S2 and S3 in the Supporting Information). Figure 2a shows the schematic band diagram of the ZnO NW demonstrating the conductive enhancement under illumination. Electron−hole pairs created under illumination lead to the excited electrons hopping into the conduction band where they contribute to the conductivity, while the holes move in the valence band simultaneously.36 Specifically, the surface, which adsorbs a negative valent molecule of functionalized layer, captures holes generated by illumination and releases electrons. The extent of band bending that occurs with respect to the light intensity depends upon charged vacancies in the depletion layer. In Figure 2b, a sketch of the energy band diagrams demonstrates a prominent Au-ZnO Schottky junction as the embedded barrier in the VRPET under forward bias. The ionized interface state tends to enhance the barrier; simultaneously, the amount of electrons, which are produced due to the separated electron−hole pairs, tend to reduce the barrier height effectively. Under forward bias, the competition between enhancement and reduction for the barrier results in a general reduction in band bending and an increase in current. Figure 2c shows the electric potential diagram of each ultraviolet OLED layer as photo gate in VRPET. The OLED in the VRPET device consists of a Au anode electrode, a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole-injection layer, a 4,4′-bis(carbazol-9-yl)-

biphenyl (CBP) hole-transporting layer, a 3-(4-biphenyl)-4phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ) light emitting layer, a 2,9-dimethyl-4,7-dipheny-l-1,10-phenanthroline (BCP) electron transporting layer, and a Ca/Al cathode.37 All the layers were successively deposited by a thermal deposition process on the patterned electrode, sequentially. Figure 2d demonstrates the typical current−voltage (I−V) curves of the PDAD/PSS functionalized ZnO NW (50 nm in diameter and 300 nm in height) under a surrounding incident light with an emission intensity of 0, 0.5, 1.0, and 5.0 mW/cm2 at 370 nm. Due to the Schottky junction, the ZnO NW channel can act as a rectifier as evidenced by the asymmetrical data shown in Figure 2d. Under forward bias conditions, the photocurrent under illumination can exceed the dark-current by 6 orders of magnitude. The photocurrent under reverse bias conditions is almost identical to the dark current. Considering the band gap properties of the ZnO and the OLED, the VRPET was designed so that the absorption spectrum of the ZnO channel and the electroluminescence (EL) spectrum of the OLED gate to matched each other to gain maximum performance. A typical absorption spectrum of the ZnO NW is portrayed in Figure 2e, and the representative EL spectrum of the TAZ OLED (in Figure 2c) is exhibited in the upper right inset of Figure 2e. The fabricated TAZ OLED which acts as the gate of the VRPET device exhibits light emission from 350 to 450 nm with a peak wavelength at 370 nm, and the ZnO NW with the 50 nm diameter exhibits an absorption peak wavelength from 360 to 380 nm. With the approaching equivalence peak of EL wavelengths and absorption, the TAZ OLED is a suitable gate for controlling the ZnO NW channel. Figure 2f shows the typical performance of the TAZ OLED where the curve presented is the light emission intensity as a function of the applied voltage. The light intensity of OLED is controllable from 0 to 0.9 mW/cm2, which satisfies the excitation condition of ZnO NW again making it suitable as the gate electrode for the VRPET. What calls for special attention are the varying characteristics the nanoscale materials exhibit when compared to with bulk C


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Figure 3. Electrical and optical characterizations of a ZnO NW-based VRPET. (a) Ids−Vgs curves of the VRPET recorded with a top, oneside, and an all-around incident light as the control gates. The inset is an illustration of the optical antenna effect in the NW. (b) Electric field intensity distribution of leaky mode resonances for ZnO NW with an incident light (λ = 370 nm) striking from the top, one-side and allaround, respectively. The upper insets are the depictions of the incident light directions. The lower insets are the distribution of the electric field intensity for typical transverse leaky modes. The black dashes are the edges of the NWs. (c) Measured spectra of the absorption efficiency for an unpolarized light obtained from individual ZnO NWs with diameters of 50 nm (blue), 140 nm (red), and 220 nm (green). (d) Calculated absorption efficiency plot of the ZnO NW channel as the function of wavelength and diameter.

materials.38 Due to the one-dimensional nature of the nanomaterial, a NW becomes an optical antenna when an incident light strikes it and causes resonance inside the NW that is based on a leaky mode resonance.39 The electromagnetic field in NW increases helping to improve the absorption of NWs.24,40 As illustrated in the inset of Figure 3a, the coupling of incident light with leaky mode resonances leads to the enhancement of light-matter interaction supported by the NWs. These NWs can be treated as antennas that catch light in circulating orbits by combining their entire inner reflections from the edge. By exploiting the leaky mode resonances to achieve optimal photodetection performance, it was found that ZnO NWs exhibit varying tunable resonant response features by altering the illumination direction. The directions chosen for the incident light to strike were the top, one-side of the NW and all-around the NW. Figure 3a presents the I−V curves of the VRPET where the same NW (50 nm diameter) channel experiences an incident light acting as the gate control terminal strikes the three different incident directions, the top, one-side and all-around. The illumination on the NW channel with the one-side and all-around incident light exhibits much a higher current response than one with the top incident light. For the one-side and all-around incidence, the transmission direction of the incident light is along the radial direction of the NW while the distribution of electric field due to resonance is concentrated on the core and surface of the NW channel. Particularly, in the all-around incidence case, the NW receives light from all directions along the radial direction which generates a stronger signal than the one-side incident case where only a portion of the light is along the radial direction. The top incident case, however, exhibits the weakest signal, poor quantum efficiency and insufficient

response due to a smaller illumination surface and shorter penetration depth. To further study the optical properties of the NW channels, resonance absorption was utilized based on leaky mode resonances for the top, one-side, and all-around incident light simulations. From Maxwell’s equations with the appropriate boundary conditions, the excitation of leaky modes occurs in a semiconductor cylinder as expressed below:39−41 y ji J′(αd) Hl′(βd) zyz jij 2 Jl′(αd) 2 Hl′(βd) z zz jj l jjn1 z jj αJ (αd) − n2 βH (βd) zzz jjj αJ (αd) − βH (βd) zzz l l l k {k l { 2 2 ij 1 1 yz i τl y = jjj 2 − 2 zzz jjj zzz jα β z{ k k { k

(1)

where α = k n12 − cos2 θ and β = k cos2 θ − n2 2 are normalized transverse wave vectors. The n1 is the fraction index related to the complex absorbing function of the ZnO NW and the n2 parameter can be treated as the effective fraction of surrounding. θ is the angle of the incident light, and τ and k are the wave vectors along the cylindrical axis and in free space, respectively. Jl is the lth order Bessel function of the first kind, and Hl is the Hankel function of the first kind, and their prime versions represent derivatives with respect to the related arguments. Two classes of equations for transverse magnetic mode (TM) and transverse electric mode (TE) can be dominated by their solutions to eq 1, respectively. The mode is labeled with the integer subscripts l and m where m is the mth root of the eigenvalue equation. The peaks in the D


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ACS Nano absorption spectra harmonize to an extraordinary number of leaky mode resonances. Based on eq 1, we simulated the direction of the incident light to strike the top, one-side and all-around the NW. The generated electric field from the NW aggregates in and around the NWs. Figure 3b shows the electric field intensity |E(r)2| for vertical ZnO NWs (50 nm in diameter, 300 nm in height) at resonant mode, which corresponds to major guide TM11 mode under an incident light of 370 nm wavelength. In the top incident light case (shown on the left in Figure 3b), the direct wave attenuates quickly and stops around the middle, indicating that carriers in the lower half of the NW cannot be excited. In the one-side incident case (middle illustration in Figure 3b), it can clearly be seen that the light striking the NW is not fully restricted within the NW. Although the incident light efficiently promotes excitation, a considerable portion of it is distributed outside the NW; this causes a relatively low light absorption in the NW. However, in the all-around incident light case (simulated with four orthogonal directions, and seen as the right-most image in Figure 3b), maximum absorption is achieved by the NW. The NW is efficiently excited by the incident light and has considerable amount of generated electric field in inside the NW. Therefore, based on the phenomenon discovered from the incident-directionselective absorption, the VRPET was designed to enhance its efficiency by using the OLED excitation light source in an allaround form. Figure 3c exhibits the absorption spectrum of the NWs with three different diameters of 50 nm (blue), 140 nm (red), and 220 nm (green) exposed to an all-around illumination. From the figure, it is obvious that the NW diameter greatly impacts the spectrum type absorbed and the amount of absorption. This is due to the resonant behavior that is exhibited at different peak wavelengths of the absorption (320, 375, and 370 nm) in the three NWs, respectively. As observed from the figure, the one with the 50 nm diameter has the highest absorption efficiency peak at 370 nm, making it suitable for the selected TAZ OLED. Figure 3d simulates the cross relationships between the absorption of the ZnO NW, the incident light wavelength, and the NW diameter. Smaller diameters of the NW provide higher peaks in the absorption spectra. Peak absorption occurs around the 370 nm wavelength for the NWs with 50 and 140 nm diameters, proving that absorption peaks at the same wavelength in different NWs may arise from different resonances.40 This resonance phenomena delivers the pathway to control and enhance the performance of NWs, which can be applied to the selection of NWs with the desired absorption and high on/off ratio for VRPET. Based on the experimental and simulation results outlined earlier, the most suitable size for the VRPET is the ZnO NW with the 50 nm in diameter is due to its similar absorption peak (at 370 nm) to that of the TAZ OLED. Following the design of the VRPET, the performance of the device needed to be systematically studied. One of the important requirements when fabricating the integrated VRPET was the ability to adjust the density of carriers in the channel with an applied bias. The corresponding transfer characteristics of the VRPET is shown in Figure 4a. VRPET adjusts its channel current by applying a gate voltage Vgs, which controls the light intensity directly and modulates the channel current with the drain voltage Vds. For a fixed driving voltage Vds = 7 V, an on-current greater than 104 nA and an off-state current of less than 0.1 nA is observed. Typically, the current

Figure 4. Local OLED gate control of the VRPET. (a) Ids−Vgs curves recorded for Vds voltages ranging from 6 to 8 V. The device completely turns off by changing the Vgs OLED voltage from 0 to 4 V. For Vds = 6 V, the Ion/Ioff ratio is greater than 105. For Vgs = 8 V, the Ion/Ioff ratio is nearly 106 with a subthreshold swing S = 75 mV/dec. (b) Ids−Vgs curves measured at different values of Vds, demonstrate that the current Ids approxiate linearly depends on voltage Vgs, indicating the excellent controlling characteristics of the VRPET. (c) Cyclic tests show the stability and fast response times ( 5 V. The on/off ratio allows the VRPET to potentially be applied in a CMOS-like digital logic device (where the required range of the Ion/Ioff ratio is between 1 × 103 and 1 × 107).42 The observed current variation at different Vgs values indicate that the photoeffect behavior of transistor is dominated by the ZnO NW channel and is controlled by the integrated TAZ OLED. At the Vds bias voltage of 8 V, the measured on-current is seen to be larger than 5 × 104 nA, with Ion/Ioff ≈ 1 × 106 and Vgs ranging from 4 to 8 V. The subthreshold slope of the VRPET is 75 mV/dec at Vds = 8 V, which is similar to the values obtained from the highperformance CdS nanobelt and 2D MoS2 transistor (74 mV/ dec).9,43 Figure 4b presents the plot of the source current Ids measured with the drain bias Vds swept from 0 to 8 V under varying Vgs voltages applied on the OLED gate. Being a direct gap semiconductor, ZnO NWs offer the attractive possibility of realizing a high conversion efficiency PET, which is better than the theoretical limit of 60 mV/dec that a classical transistor exhibits.9 This attribute is particularly evident in indirect gap E


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Figure 5. Electromagnetic interference experiments for VRPET and Si-FET. (a) I−V characteristics for VRPET (orange dots) and Si-FET (green dots) under an electromagnetic interference (EMI, yellow zone) for a period of time. Vds of VRPET is 6.0 V; Vds of Si-FET is 1.5 V. (b) Output current of the VRPET (orange line) and Si-FET (green line) under a strong periodic high voltage pulse (marked as flash symbols) periodically. The results of (a) and (b) clearly show that VRPET possesses a constant operation under electromagnetic action, when compared to the Si-FET.

A large-scale integrated device of a 10 × 10 VRPET array was fabricated to boost the electric output for large current control. Figure 6a illustrates an SEM image of the 10 × 10 VRPET array with an interval of 2.5 μm, where devices of the VRPET array share the same drain, source and gate electrodes. The source electrode forms the bottom layer while the drain/ gate electrodes from the top layer. The inset is the SEM image enlarged to show four VRPETs. To test the electrical performance of the VRPET array, OLED array as gates is applied to control the VRPET array, as shown in Figure 6b. As evidenced by the figure, it is clearly seen that, by connecting the array of devices in parallel, the combined outputs of the 10 × 10 VRPET array has on-current higher than 40 mA and an off-current below 1 μA (Vgs = 6 and 0 V, respectively; Vds = 6 V). The improved output current of the VRPET array is associated with an increase in the component number. The response time of the 10 × 10 VRPET array remains the same as that of a single VRPET, an advantageous quality. Figure 6c presents the loading test results of the studied 10 × 10 VRPET array devices. When the voltage Vds increases from 7 to 16.5 V, the source current Ids increases from 40 to 150 mA, quasilinearly. When Vds is larger than a threshold of 16.5 V, the device is overloaded and an irreversible fusing occurs; a state caused by chain-fusing. This property can allow the VRPET array to be used as stable current controllers and circuit protection systems, proving possibilities to power nanodevices and photocontrol electronics. Despite power consumption being relatively higher than the Si FET, because OLED as gate needs to transfer electric energy to light for controlling the carriers in the NW channel, the Si FET directly controls the channel by electric field. The VRPET can still lead to practical applications on large-scale array devices.

materials, because their interband transitions need extra phonons and reconstruction centers. The direct gap transistor, realized by a NW as the channel, can easily be controlled by a diminutive integrated OLED gate that exhibits an Ion/Ioff ratio of about 106, which is comparable to an Si-FET. Figure 4c reveals the cyclic working property of the VRPET controlled by the OLED as gate under the bias Vds = 6 V, which is recorded with Vgs = 6 V (OLED ON) and 0 V (OLED OFF). The figure demonstrates the VRPET’s ON and OFF states. It is proven from the figure that the VRPET can be reversibly switched between low and high source currents. The rise and fall times are each within 50 ms. As a device, one of the applications of the VRPET is its capability to resist electromagnetic disturbance.44 The VRPET stands as a good solution to the EMI due to its special design and the type of materials used. From the design aspect, the OLED of the VRPET, which possesses fixed electromagnetic properties, is applied as the gate so that the carriers of the device are directly excited by photons which are immune to electromagnetic signals, as opposed to the carriers in Si-FET which are controlled by an electrical field. When it comes to the materials employed, the ZnO NW is a wide band gap semiconductor (3.37 eV) with outstanding electrical and optical properties that possesses a much better antiinterference performance compared to the Si (band gap 1.1 eV). Figure 5a shows the comparison between the VRPET and a Si-FET (specifically, FK3306010L Panasonic) I−V characteristics under EMI (where the intensity of the oscillating voltage is about 104 V/m). VRPET exhibits the same continuous electric property with a smooth output curve controlled by the gate bias with EMI (Figure 5a) and without EMI (Figure 4a). Conversely, the Si-FET presents an obvious disturbance in the presence of an EMI. In Figure 5b, the continuous output signal response of a periodic voltage pulse (≃105 V/m) applied to both VRPET (orange line) and Si-FET (green line) is presented. The apparent random signal spikes in Si-FET are observed when the voltage pulse is applied. On the other hand, the VRPET remains unperturbed by the EMI, thus keeping an invariable output current. From the discussed results, the VRPET system remains at a high steady status under EMI compared to the Si-FET, which is one of the advantages for having a photocontrol device in contrast to an electric-fieldcontrol device.

CONCLUSIONS In all, we have reported a fully functional component device, VRPET with an all-around OLED as gate control, that establishes possibilities for numerous innovative applications. The design established which integrates a wide and direct band gap vertical NW and an OLED device gives rise to an excellent EMI resistance. The properties of the VRPET can help researchers gain a better understanding of the photogenerated controllable process, and promote large-scale fabrication to improve uniformity. Additionally, the high performance F


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MOCVD is prepared as mentioned in ZnO film synthesis. Next, PMMA resists are spin-coated, and EBL is performed to form 50 nm dot in diameter. (The EBL process can also be replaced by a similar fabricating process with a high-precision mask aligner.) The top Au metal is fabricated using sputtering through a lift-off process as mask. The prefabricated wafer is dry-etched using RIE with H2/Ar/CH4 mixed gas under the flow rates of 9 sccm/9 sccm/24 sccm, respectively. Furthermore, the ZnO NW is clad by spin-coating PDAD, PSS, and PMMA layer in sequence. Then the wafer is processed by EBL and cleaned by plasma cleaner to remove the redundant material. Then, the OLED is developed as mentioned in OLED fabrication process. The Au top electrode is fabricated using magnetron sputtering and etched by RIE to be the source and gate electrode. Finally, the sample is protected by SiO2 and electrical connections are established among the drain, source, and gate electrode.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsnano.9b04163. Materials and methods such as ZnO NWs synthesis by MOCVD, EBL, and dry etching process for OLED and VRPET fabrication process; TEM image of functionalized ZnO NW; characteristics of VRPET for on/off ratio and response; schematic and SEM image of device with VRPET arrays; LMR for dependent position on the normal incident; cyclic test and anti-electromagnetic interference test for VRPET (PDF)

AUTHOR INFORMATION Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Qikun Li: 0000-0002-7065-5032 Chengming Jiang: 0000-0003-2779-5774 Jinhui Song: 0000-0002-0042-2014 Figure 6. Large-scale array integration of 10 × 10 VRPETs. (a) SEM image of the large-scale device composed of 100 VRPETs (10 × 10 array). The inset is the enlarged SEM image of four VRPETs. (b) Multicycle source current response Ids of the VRPET array under the control of OLED matrix gates. The drain current response is significantly enlarged by the parallel connection of the individual VRPETs. Both on/off ratio and response speed still possess the same properties as a single VRPET. (c) Loading test of the VRPET array. Plot of current Ids versus the applied voltage Vds, revealing the loading and overloading current change with the applied voltage in the 7−19 V range.

Author Contributions ⊥

Q.K.L. and S.B. contributed equally to this work.

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS This project is financially supported by Science Fund for Creative Research Groups of NSFC (51621064), National Natural Science Foundation of China (NSFC, 51702035 and 51602056), Dalian University of Technology, China, (DUT16RC(3)051), and Science and Technology Project of Liaoning Province 20180540006.

nanoscale VRPET exhibits a step forward in creating fully integrated optoelectronics circuits for on-chip technologies. With the possibility of manufacturing large-scale circuits, our results could be utilized extensively in producing photoelectronics that combine the device processes discussed coupled with organic−inorganic materials.

REFERENCES (1) Sze, S. M.; Ng, K. K. Physics of Semiconductor Devices; John Wiley & Sons, Inc.: Hoboken, NJ, 2006. (2) Waldrop, M. M. More Than Moore. Nature 2016, 530, 144− 147. (3) Frank, D. J.; Dennard, R. H.; Nowak, E.; Solomon, P. M.; Taur, Y.; Wong, H. S. P. Device Scaling Limits of Si MOSFETs and Their Application Dependencies. Proc. IEEE 2001, 89, 259−288. (4) Vashchenko, V. A.; Sinkevitch, V. F. Physical Limitations of Semiconductor Devices; Springer US: Boston, MA, 2008. (5) Flack, T. J.; Pushpakaran, B. N.; Bayne, S. B. GaN Technology for Power Electronic Applications: A Review. J. Electron. Mater. 2016, 45, 2673−2682.

METHODS Silicon dioxide (SiO2) is grown to be roughly a 300 nm thick film on standard silicon wafer (substrate ⟨100⟩ orientation) as a flat insulator layer in tube furnace. The PMMA resist is spin-coated on the precleaned wafer, and EBL is performed as the designed layout. The wafer is developed followed with Ca/Al (30 nm) fabricated using a thermal evaporating and lift-off process. Then a ZnO layer grown by G


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High Performance Vertical Resonant Photo-Effect-Transistor with an

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