Vertical InGaAs Nanowire Array Photodiodes on Si - ACS Photonics

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Vertical InGaAs nanowire array photodiodes on Si Kohei Chiba, Akinobu Yoshida, Katsuhiro Tomioka, and Junichi Motohisa ACS Photonics, Just Accepted Manuscript • DOI: 10.1021/acsphotonics.8b01089 • Publication Date (Web): 01 Feb 2019 Downloaded from http://pubs.acs.org on February 2, 2019

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Vertical InGaAs nanowire array photodiodes on Si Kohei Chiba, Akinobu Yoshida, Katsuhiro Tomioka, and Junichi Motohisa∗ Graduate School of Information Science and Technology and Research Center for Integrated Quantum Electronics (RCIQE), Hokkaido University, North 14 West 9, Sapporo 060-0814, Japan E-mail: [email protected] Phone: +81 11 706 6508. Fax: +81 11 716 6004 Abstract We demonstrated vertical InGaAs nanowire (NW) array photodiodes on Si, which were optically responsive to visible light (635 nm) and near-infrared light around 1.55 µm. The vertical NWs were directly grown on Si by selective-area growth. Implementation of a heavily Sn-doped contact layer in the InGaAs NWs improved the diode characteristic owing to lower series resistance and, as a result, a photoresponsivity of 0.25 A/W was obtained at 635 nm, which was twice that before the improvement. Moreover, InGaAs/InP core-shell NWs increased the photocurrent density about 20-fold under the illumination of light in the 1.55 µm wavelength band owing to suppression of surface recombination. These findings are expected to be useful for NW-based photovoltaic applications for optical interconnection and Si platforms.

Keywords nanowire, photodiode, InGaAs, Si, selective-area growth, metalorganic-vapor phase epitaxy 1

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The integration of III-V compound semiconductor optical devices on a silicon (Si) platform has been attracting considerable attention as an approach to the optical intraconnection and interconnection of integrated circuits. 1–3 Since Si is an indirect-gap semiconductor and transparent in the optical fiber telecommunication bands, heterogeneous integration with more optically active materials at the corresponding wavelengths is required, and III-V semiconductors are ideal materials since they are suitable for both light emitters and photodetectors. In this context, the heteroepitaxy of III-V semiconductors on Si is the most straightforward approach to device integration. However, it is difficult to suppress crystal defects due to mismatches in the lattice constant and thermal expansion coefficient between III-V semiconductors and Si in the case of integration in a planar structure. On the other hand, the direct epitaxy of III-V semiconductor nanowires (NWs) on Si has been widely studied to as a means of relaxing the lattice mismatch and strain between NWs and Si and to integrate high-quality III-V semiconductors directly on a Si platform. 4–6 Vertical III-V NWs are expected to be applied to nanoscale light sources and detectors owing to their geometrical advantages such as a large surface area, a dense array structure enabling efficient light trapping, and a small footprint. 7–9 In addition, a core-shell structure can be implemented, in which the heterojunction is formed on the NW sidewalls, to improve the optical characteristics owing to surface passivation. 10,11 Among the III-V NWs, InGaAs NWs have high electron mobility and their band gap energy can cover a wide range from the nearinfrared to visible range by varying their alloy composition, and they are widely used in conventional optoelectronic devices, such as lasers, 12 photovoltaics, 13 and field-effect transistors. 14 In addition, an InGaAs photodetector (PD) exhibits a smaller leakage current than InAs and Ge PDs and achieves high sensitivity in the near-infrared region including the optical telecommunication bands. 15,16 Although InGaAs NW/Si photovoltaic cells have been demonstrated, 13,17 there has been little investigation of the use of InGaAs NW PDs on Si for the optical telecommunication bands and Si photonics. In this study, we demonstrate PDs using vertical InGaAs NW arrays directly grown on Si and show their operation under

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visible and 1.55-µm-wavelength illumination at room temperature. We also describe some methods to improve the performances of PDs, which are also applicable to other NW-based devices. For the integration of NWs, p-Si(111) substrates (resistivity 2–4 Ω·cm, with B-doping of 3 to 8×1015 cm−3 ) partially masked with 20-nm-thick SiO2 were prepared by thermal oxidation, electron-beam lithography, and wet chemical etching. InGaAs NWs with an axial p-i-n junction were grown by selective-area growth using trimethylgallium (TMGa), trimethylindium (TMIn), and arsine (AsH3 ). Silane (SiH4 ) and diethylzinc (DEZn) were used as n-type and p-type dopants, respectively. To be precise, the i-region is not considered to be intrinsic and refers to unintentionally doped layer, and is highly likely to be doped with Zn, which was brought forth by diffusion, 18 or residual donors (mainly Si). To adjust the absorption edge to around 1.55 µm, we designed the solid-phase composition of In in InGaAs NWs to be 51–53%. For this purpose, the composition of In in the vapor phase (ratio of TMIn supply to the total TMIn and TMGa supply) was set at 41% because the In content in InGaAs NWs is known to be larger than that in the vapor phase under our employed growth conditions. 19 The V/III partial pressure ratio was 112 and the growth temperature was 670 ◦ C. Prior to the NW growth, control of the surface polarity in accordance with previous reports 14,20 was employed to align vertical InGaAs NWs. Figure 1a shows a scanning electron microscope (SEM) image of the vertical InGaAs NW array with an axial p-i-n structure on p-Si(111) grown by selective-area growth. The pattern pitch, NW diameter, and NW height were 600 nm, 130 nm, and 1.4 µm, respectively. The heights of the p, i, and n layers in the InGaAs NWs estimated from the growth rate were approximately 600 nm, 400 nm, and 400 nm, respectively. Formation of the axial p-i-n InGaAs NWs are reported by Nakai et al. 21 and, since we carried out the growth under the similar conditions, the present NW also expected to have axial p-i-n structures. More details of the growth process as well as doping scheme are described in the supporting information. Next, we fabricated the vertical InGaAs NW-array PD illustrated in Figure 1b. The NW

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array was buried with benzocyclobutene (BCB) then the BCB was removed by reactive ion etching (RIE) using CH4 and O2 to expose the top parts of the NWs for use as contacts. Then, a transparent 2-nm-thick Ti/100-nm-thick indium tin oxide (ITO) multilayer was deposited on the NWs, and 100-nm-thick Al was deposited on the underside of the p-Si substrate. The purpose of the thin Ti layer was to reduce the contact resistance between the ITO and the III-V semiconductor. 21 Figure 1c shows an optical microscopic image of the NW-array PD, in which about 7000 NWs were integrated in the 50 × 50 µm2 device area S. Currentvoltage characteristics of the PD were measured by using standard source-measure units with and without focused laser light of various wavelengths irradiated normal to the PD. The current and photocurrent density was calculated by dividing measured current with S. For photocurrent measurement in the visible range, we used Thorlabs S1FC635 fiber coupled laser source, and Agilent 86100B tunalbe laser source for photocurrent spectrum measurement in the telecommunication band. Figure 2a shows the current density-voltage (J–V ) characteristics of the vertical InGaAs NW-array PD at room temperature with and without illumination. According to the J–V characteristic obtained in the dark, the device showed moderate rectifying properties and its turn-on voltage was 0.4 V. The ideality factor was 6.5 and dark current was approximately 0.20 mA/cm2 at −1 V. Under the illumination of a diode laser (∼ 635 nm, power 0.2 mW/cm2 ), the photocurrent density was approximately 0.015 mA/cm2 at zero bias, meaning that the NW-array PD on Si optically responded to visible light. At present, the ideality factor did not have a moderate value (1–2), and the series resistance calculated from the J–V characteristic was 1.06 Ω · cm2 ; these values are considerably larger than those of conventional PDs. One of the reasons for the large values was the large series resistance at the junction between the InGaAs NWs and Si and/or the Ti/ITO electrode and the NWs. In particular, formation of backward diodes at these junctions largely deteriorates the ideality factor. 22 On the other hand, shunt resistance of the diode was estimated from dJ/dV at V = −1.5 V and was about 1.0 × 104 Ω · cm2 , which was four orders of magnitude larger

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than the series resistance. Figure 2b shows the photocurrent density dependence on the illumination power density under a bias of −1 V. A moderate linear relationship was obtained between the photocurrent density and the illumination power density. The photoresponsivity at a wavelength of 635 nm was 0.13 A/W. Figure 2c shows the photocurrent spectrum at zero bias in the 1.55 µm wavelength band indicating the PD responses in the C-band. The photocurrent spectrum had a peak at around 1.5 µm. This is similar to the results reported in Ref. 26 for a single InGaAs NW photoconductive photodetector, but the its origin is not identified yet. From the Tauc plot, the absorption edge was determined to be 0.761 eV. This indicates that the InGaAs NWs with an In content of about 51–52% formed on Si operate as a light-absorbing layer and the designed composition of the NWs was realized. Note this estimation may contain error due to complicated absorption spectrum originating from the three-dimensional nanostructure array but this value is fairly consistent with our designed In content of InGaAs NWs (51–53%). However, the photocurrent density in the C-band is very small, and is about five orders of magnitude smaller than that in the case of visible-light illumination. The major reason for this difference is in the light absorption in Si; that is, the photogenerated carriers in Si contribute to the photocurrent under 635 nm irradiation. It is not clear if photogeneration in Si leads to zero-bias photocurrent owing to the near-by junction between Si and InGaAs, but photocurrent through the NW-PD should increase owing to the photogenerated carriers in Si. In addition, it is considered to that the light absorption is small in InGaAs NWs in the C-bands, as will be explained later. The recombination of the photogenerated carriers in the surface of InGaAs NWs is also thought to be one of the reasons for the poor photoresponse in the C-band. To improve the characteristics and performance of the PD, two approaches were introduced for the NW structures. Note that these approaches are generally applicable to various NW-based devices. First, a heavily Sn-doped n+ -InGaAs contact layer was formed in the InGaAs axial pi-n junction NW to reduce the contact resistance between the NWs and the Ti/ITO electrode. Since the amount of Si dopant is likely to be insufficient to form an n+ contact layer,

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tetraethyltin (TESn) was used as the Sn dopant. To suppress the lateral overgrowth of NWs by excess Sn atoms and maintain good uniformity of the InGaAs NWs, an n+ -InGaAs contact layer with thickness of about 200 nm was grown by pulse doping. 23,24 The J–V characteristics of the InGaAs NW-array PD with the contact layer in Figure 3a showed steep turn-on characteristics. The series resistance was about 0.0345 Ω · cm2 , which was lower than that without the contact layer by a factor of 30.7, and the ideality factor was decreased from 6.5 to 3.8. As shown in the logarithmic plot of the inset, the reverse leakage current increased also by two order of magnitude. Nevertheless, the shunt resistance was estimated to be 6 × 102 Ω · cm2 and was more than four orders of magnitude larger than the series resistance. Therefore, it clearly does not degrade the characteristics of the diode. The J–L curve in Fig. 3b confirmed the linear relationship and a photoresponsivity of 0.25 A/W was obtained under a reverse bias of −1 V. Thus, the responsivity was twice that for the case shown in Fig. 2. Quantum efficiency η of the photodetector is given by 9,25

η=

qRλ hc

(1)

where R the photoresponsivity, λ the detecting wavelength, q the electron charge, h the Planck constant, and c the speed of the light in vacuum. Using λ=632.5 nm and R = 0.25 W/A, we get η =12.8 %. The photocurrent density in the C-band also increased by factor of 2 owing to the heavily doped contact layer, meaning that the conversion efficiency of the PD was improved by the low contact resistance. Next, an InP shell layer was grown on the InGaAs axial p-i-n junction NW to reduce the surface recombination of NWs, It is known that the lattice constant of the InP shell matches that of the InGaAs NW when the In composition is 53%. As schematically shown in Figure 4a, the InP shell layer was grown to a thickness of about 10 nm in the radial direction to form the InGaAs/InP core-shell NWs. To facilitate shell growth, 27,28 V/III material supply ratio was set higher and the growth temperature was lowered to 580 ◦ C

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after the growth of InGaAs NWs (see supporting information for detail). Considering the In composition in the core (about 50–51%) and the thickness of the InP shell, the coherency of the lattice in the whole NWs was maintained and the InGaAs core was subject to the tensile strain. Figure 4a shows a schematic illustration of the InGaAs-InP core-shell NW-array PD, whose InP thickness was about 10 nm in the radial direction. In the device process, the InP layer on the top of the NWs was etched by RIE to form Ohmic contacts between the n+ -InGaAs layer and the Ti/ITO electrode. Etching of InP was carried out using using CF4 and O2 after the etching of BCB, but the etching condition was different from that used for BCB. Figure 4b shows the photocurrent density spectra of the InGaAs-InP coreshell NW-array PDs at zero bias in the 1.55 µm wavelength band. The spectrum for the core-shell NWs shifted to a longer wavelength by about 10 nm. This is partly due to the tensile strain in the InGaAs core. To estimate the amount of strain and energy shift, we calculated the strain assuming cylindrical symmetry in cylindrical core shell structure 29 and corresponding shift of the band edge energy using standard theory based on orbital-strain Hamiltonian. Detail of the calculation procedure is described in the supporting information. In the present core-shell structure with In composition of 51% in InGaAs, strain ϵzz in the core was calculated to be 5 × 10−4 , which leads to a redshift of the optical transition energy by about 5nm. More importantly, the photocurrent density was increased about 20-fold, meaning that the InP shell layer passivated the InGaAs NWs and effectively suppressed the surface recombination process in the InGaAs NWs. Therefore, we succeeded in increasing the extraction of photogenerated carriers in the InGaAs-NW array PDs. Thus, the InP shell layer is expected to improve the photoresponse in the optical telecommunication bands. As described above, introduction of the contact layer greatly improved the ideality factor of the diode, but it is still much far from unity. This could be due to the formation of backward diodes, 22 tunneling or carrier recombination through defects (presumably at the junction between NWs and Si substrates), and surface recombination which is not completely suppressed by the shell layer. These unwanted factors should degrade the performance of

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photodiodes, thus, it is necessary to clarify and eliminate the limiting factors. Furthermore, the photoresponsivity in the 1.55 µm wavelength band for the InGaAs-InP core-shell NWs was about 3 µA/W, which is about five orders of magnitude smaller than that at the visible wavelength of 635 nm. This is probably because the light absorption by the InGaAs NW array was still insufficient, which was due to the mismatch of the NW pitch (about 600 nm) and the corresponding wavelength (1.5 µm) and to the small diameter of the NWs. Thus, it is necessary to design and optimize the period, diameter, and height of the NWs. Our preliminary investigation shows that optimal absorption at 1.55 µm can be achieved for a = 1.0 ∼ 1.3 µm and d/a = 0.23 ∼ 0.3, and detail will be described elsewhere. Optimization of the thickness of each p-i-n layer is also required to further improve the performance of NW PDs in both the visible and optical telecommunication bands. In conclusion, we demonstrated InGaAs NW-array PDs on Si substrates. The photoresponses at room temperature under illumination at 635 nm and around 1.55 µm were obtained. The photocurrent linearly increased with the laser intensity and the photoresponsivity at a wavelength of 635 nm was measured to be 0.13 A/W under a reverse bias of −1 V. The contact resistance between the NWs and Ti/ITO was reduced by implementing a heavily Sn-doped contact layer, and the diode characteristics were improved and the photoresponsivity was increased about twofold. Moreover, the passivation effect of the core-shell structure was found to be effective in increasing the photocurrent density in the 1.55 µm wavelength band. These PDs are expected to be used as Si-photonic optical devices enabling optical interconnection in integrated circuits and information communications in the optical telecommunication bands.

Acknowledgement The authors acknowledge Prof. Tamotsu Hashizume and Prof. Yasuhiko Ishikawa for fruitful discussions and Dr. Fumiya Ishizaka for his experimental support. This work was finan-

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cially supported by Grants-in-Aid for Scientific Research from MEXT (Grant No.16K14221, No.16H06080, and No.17H03223).

Supporting Information Available The following files are available free of charge. • Filename: suppinfo.pdf

References (1) Tanabe, K.; Watanabe, K.; Arakawa, Y. III-V/Si hybrid photonic devices by direct fusion bonding. Sci. Rep. 2012, 2, 349. (2) Gao, Y.; Zhong, Z.; Feng, S.; Geng, Y.; Liang, H.; Poon, A. W.; Lau, K. M. HighSpeed Normal-Incidence p-i-n InGaAs Photodetectors Grown on Silicon Substrates by MOCVD. IEEE Photonics Technol. Lett. 2012, 24, 4. (3) Inoue, D.; Lee, J.; Doi, K.; Hiratani, T.; Atsuji, Y.; Amemiya, T.; Nishiyama, N.; Arai, S. Room-temperature continuous-wave operation of GaInAsP/InP lateral-currentinjection membrane laser bonded on Si substrate. Appl. Phys. Express 2014, 7, 72701. (4) Glas, F. Critical dimensions for the plastic relaxation of strained axial heterostructures in free-standing nanowires. Phys. Rev. B 2006, 74, 121302. (5) 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. (6) Koblmüller, G.; Abstreiter, G. Growth and properties of InGaAs nanowires on silicon. Phys. Status Solidi RRL 2014, 8, 11–30.

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(7) Yan, R.; Gargas, D.; Yang, P. Nanowire photonics. Nat. Photonics 2009, 3, 569–576. (8) Motohisa, J.; Hiruma, K. Light absorption in semiconductor nanowire arrays with multijunction cell structures. Jpn. J. Appl. Phys. 2012, 51, 11PE07. (9) LaPierre, R. R; Robson, M.; Azizur-Rahman, K. M.; Kuyanov, P. J. Phys. D: Appl. Phys. 2017, 50, 123001. (10) Garnett, E. C.; Yang, P. Silicon Nanowire Radial p-n Junction Solar Cells J. Am. Chem. Soc. 2008, 130, 9224. (11) Dimakis, E.; Jahn, U.; Ramsteinger, M.; Tahraoui, A.; Grandal, J.; Kong, X.; Marquart, 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. (12) 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. (13) Shin, J. C.; Kim, K. H.; Yu, K. J.; Hu, H.; Yin, L.; Ning, C.-Z.; Rogers, J. A.; Zuo, J.-M.; Li, X. Inx Ga1−x As nanowires on silicon: one-dimensional heterogeneous epitaxy, bandgap engineering, and photovoltaics. Nano Lett. 2011, 11, 4831–4838. (14) Tomioka, K.; Yoshimura, M.; Fukui, T. A III-V nanowire channel on silicon for highperformance vertical transistors. Nature 2012, 488, 189. (15) Wei, W.; Bao, X.-Y.; Soci, C.; Ding, Y.; Wang, Z.-L.; Wang, D. Direct Heteroepitaxy of Vertical InAs Nanowires on Si Substrates for Broad Band Photovoltaics and Photodetection. Nano Lett. 2009, 9, 2926–2934. (16) Otuonye, U.; Kim, H. W.; Lu, W. D. Ge nanowire photodetector with high photoconductive gain epitaxially integrated on Si substrate. Appl. Phys. Lett. 2017, 110, 173104. 10


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(17) Treu, J.; Stettner, T.; Watzinger, M.; Morkötter, S.; Döblinger, M.; Matich, S.; Saller, K.; Bichler, M.; Abstreiter, G.; Finley, J. J.; Stangl, J.; Koblmüller, G. Lattice-Matched InGaAs-InAlAs Core-Shell Nanowires with Improved Luminescence and Photoresponse Properties. Nano Lett. 2015, 15, 3533–3540. (18) Li, Z.; Yang. I.; Li, L.; Gao, Q.; Chong, J. S.; Li, Z.; Lockrey, M. N.; Tan, M. H.; Jagadish, C.; Fu, L.; Reducing Zn diffusion in single axial junction InP nanowire solar cells for improved performance. Prog. Nat. Sci.: Mat. Intern. 2018, 2, 178–182. (19) Chiba, K.; Tomioka, K.; Yoshida, A.; Motohisa, J. Composition controllability of InGaAs nanowire arrays in selective area growth with controlled pitches on Si platform. AIP Advances 2017, 7, 125304. (20) Tomioka, K.; Tanaka, T.; Hara, S.; Hiruma, K.; Fukui, T. Composition controllability of InGaAs nanowire arrays in selective area growth with controlled pitches on Si platform. IEEE J. Sel. Top. Quantum Electron. 2011, 17, 1112. (21) Nakai, E.; Yoshimura, M.; Tomioka, K.; Fukui, T. GaAs/InGaP Core-Multishell Nanowire-Array-Based Solar Cells. Jpn. J. Appl. Phys. 2013, 52, 055002. (22) Shah, J. M.; Li, Y.-L.; Gessmann Th.; Schubert E. F. Experimental analysis and theoretical model for anomalously high ideality factors (n ≫ 2.0) in AlGaN/GaN p-n junction diodes. J. Appl. Phys. 94 (2003) 2627. (23) 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. (24) Nakai, E.; Chen, M.; Yoshimura, M.; Tomioka, K.; Fukui, T. InGaAs axial-junction nanowire-array solar cells. Jpn. J. Appl. Phys. 2015, 54, 015201.

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(25) Sze S. M.; Ng K. K. Physics of Semiconductor Devices. Third Ed., Wiley-Interscience, John Wiley & Sons,: New Jersy, 2007; p. 666. (26) Tan, H.; Fan, C.; Ma, L.; Zhang, X.; Fan, P.; Yang, Y.;Hu, W. ;Zhou, H.;Zhuang, X.; Zhu, X.; Pan, A. Single-Crystalline InGaAs Nanowires for Room-Temperature HighPerformance Near-Infrared Photodetectors. Nano-Micro Lett. 2016 29–35. (27) 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. (28) 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. (29) Trammell, T. E.; Zhang, X.; Li, Y.; Chen, L.-Q.; Dickey, E. C. Equilibrium strainenergy analysis of coherently strained core-shell nanowires. J. Cryst. Growth 2008, 310, 3084.

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(a)

(b)

(c)

Figure 1: (a) 30◦ -tilted SEM image showing the vertical InGaAs NW array with an axial p-i-n junction on p-Si(111). (b) Schematic illustration of the vertical InGaAs NW-array PD. (c) Optical microscopy image of the PD. About 7000 NWs were integrated in the black region (50 × 50 µm2 )

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(a)

(b)

(c)

Figure 2: (a) J–V characteristics at room temperature in dark and under illumination using a diode laser (635 nm). (b) Photocurrent density dependence on illumination power density at 635 nm wavelength under reverse bias of −1 V. (c) Photoresponse spectrum at zero bias in the 1.55 µm wavelength band. 14


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(a)

Sn contact layer

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J (A/cm )

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10

-3

10

-7

-1

0 V (V)

1

(b)

Figure 3: J–V characteristics of the NW-array PDs with and without a heavily Sn-doped n+ -InGaAs contact layer. The insets show a schematic illustration of the PD using the InGaAs NWs containing the contact layer and logarithmic plot of J–V characteristics. (b) Photocurrent density dependence on illumination power density at 635 nm wavelength under reverse bias of −1 V.

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(a)

(b)

Figure 4: (a) Schematic illustration of the InGaAs-InP core-shell NW-array PD. (b) Photocurrent spectra of the fabricated PDs with and without the InP shell layer.

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ACS Photonics

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ACS Photonics

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Sn contact layer

10

2

1

10

-1

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-5

J (A/cm )

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ACS Photonics

10

-3

10

-7

-1

0 V (V)

1


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ACS Photonics


Vertical InGaAs Nanowire Array Photodiodes on Si - ACS Photonics

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