See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/318171007 Near-Infrared-Light Photodetectors Based on One-Dimensional Inorganic Semiconductor Nanostructures Article in Advanced Optical Materials June 2017 DOI: 10.1002/adom.201700081 CITATIONS 5 READS 208 4 authors, including: Lin-Bao Luo Hefei University of Technology 135 PUBLICATIONS 4,280 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Reproducible Surface Enhanced Raman Spectroscopy (SERS) of DNA based on Si nanopillars View project Low-dimensional Plasmonic Photodetectors View project All content following this page was uploaded by Lin-Bao Luo on 18 September 2017. The user has requested enhancement of the downloaded file.
Review Photodetectors Near-Infrared-Light Photodetectors Based on One-Dimensional Inorganic Semiconductor Nanostructures Feng-Xia Liang, Jiu-Zhen Wang, Zhi-Peng Li, and Lin-Bao Luo* Recently, near-infrared light photodetectors (NIRPDs) have attracted increasing interest due to their promising applications in both military and civil purposes. One-dimensional inorganic semiconductor nanostructures (NSs) have unique electrical and optical properties and have been widely used to fabricate many NIRPDs. These prototype devices have geometries ranging from photoconductive-type photodetectors and metal semiconductor Schottky junction photodetectors to nano-heterojunction photodetectors. They have good device performance including high responsivity and specific detectivity, fast response speed, low power consumption, etc. Here, we will review the state-of-the-art advance in the fabrication of 1D semiconductor NSs for NIRPD application. We first briefly survey recent progress in the growth and fabrication methodologies including both bottom-up and topdown approaches. We also highlight the achievement in this flourishing field by sketching device fabrication, comparing the device performance, and discussing the operation mechanism. Finally, we close with unresolved issues and challenges. 1. Introduction Infrared (IR) light is a type of electromagnetic wave with wavelength from 780 nm to 1 mm. IR light can be divided into three regions: near-infrared (NIR) from 0.78 to 3.0 µm, mid-infrared (MIR) from 3.0 to 50 µm, and far-infrared (FIR) from 50 to 1000 µm. [1] Due to its wide applications in imaging, medical diagnosis, and industrial equipment monitoring, NIR has received extensive research interest worldwide. [2,3] For example, spectral imaging technology including multispectral imaging in the NIR region is a very useful and non-destructive method to analyze ancient paintings most pigments are transparent in this region and its different reflectance changes in the NIR range. [4] In addition, by replacing traditional electrical cables with optical fibers, light-wave technology using NIR (1310, and 1528 1620 nm) not only increases the information carrying Dr. F.-X. Liang, J.-Z. Wang School of Materials Science and Engineering Hefei University of Technology Hefei 230009, China Z.-P. Li, Prof. L.-B. Luo School of Electronic Science and Applied Physics Hefei University of Technology Hefei 230009, China E-mail: luolb@hfut.edu.cn DOI: 10.1002/adom.201700081 capacity, but also speeds up data transmission rate. [5] These NIR-based technologies have spawned various highly sensitive NIR detectors (NIRPD). [6] Generally, NIRPDs can be classified into three categories based on differences in mechanism: thermal detectors, radiation field detectors, and photon detectors. [7] The photon detector takes advantage of the photoelectric effect of semiconductors. It can directly transform electromagnetic radiation into electrical signals. [8] The past decade has witnessed a progressive miniaturization of NIRPDs driven by rapid nanoscience and nanotechnology. [9 11] Versus NIRPDs based on traditional thin films and bulk materials, NIRPDs based on low dimensional semiconductor nanostructures particularly one dimensional nanostructures (e.g., nanowire (NW), nanorods (NR), nanobelts (NB), etc.) usually have high responsivity and specific detectivity, fast response, high on-off ratio, broad response or high spectral selection, good flexibility, and low energy consumption. [12 14] There are two reasons for this behavior. [15,16] First, onedimensional nanostructures (1D NSs) usually have a large surface-to-volume ratio that can increase the number of surface trap states and prolong the photocarrier lifetime. Second, the reduced dimensionality can also restrict the active area of the charge carrier, and this can greatly shorten the transit time during photoelectric processes. [17] Moreover, due to their small dimensions and good compatibility with semiconductor technology, nano-nirpds facilitate highly integrated and miniature devices which are critical for the development of high-performance optoelectronic systems. [17] To date, many growth strategies have been successfully developed to obtain 1D semiconductor NSs with well-controlled electrical property, morphology, chemical composition, and crystallinity. These strategies include top-down methods (e.g., electron beam lithography, chemical etching, and reactive ion etching) as well as bottom-up methods (thermal evaporation, chemical vapor deposition (CVD), plasma enhanced CVD, metalorganic CVD, hydrothermal reaction, and solution-mediated vapor liquid solid method). In accordance with their difference in chemical composition, semiconductor NSs suitable for NIR detection can be classified into three groups. [18 21] The first one is group IV elements including silicon (Si), germanium (Ge) and carbon nanotubes (CNTs). The III-V group 1700081 (1 of 14)
contains some of narrow band-gap semiconductor materials such as indium phosphide (InP), indium arsenide (InAs), gallium arsenide (GaAs), gallium antimony (GaSb), and ternary III-V materials (InGaAs). [22] The third group includes emerging semiconductors such as Bi 2 S 3 and Bi 2 Se 3 in the V-VI group and GeSe and SnS 2 in the IV-VI group. Although some semiconductors nanostructures based on In 2 Se 3, SiGe alloy, Cd 3 P 2, and ternary PbSnTe, etc. are suitable for infrared photodetection, they are relatively rare and excluded from further discussion. To gain a straightforward insight into these 1D semiconductors nanostructure-dependent photosensitivity, we tabulate representative device parameters of 1D inorganic NSs based NIRPDs. Table 1 shows nano-nirpds with different device geometries including photoconductive-type photodetectors, metal-semiconductor Schottky junction photodetectors, and nano-heterojunction (p-n, and p-i-n) systems, which have been constructed in recent years. The photoconductive-type NIRPD normally exhibits a relatively high photoconductive gain but relatively slow response speed, while the Schottky junction NIRPDs or nano-heterojunction NIRPDs are often characterized by relatively high on/off ratio, low energy consumption, and fast response speed. [23,24] This article presents a brief summary of the current research that focuses on 1D inorganic semiconductor NSs NIRPDs. We will discuss several types of semiconductor materials by groups which are listed above. Each section will begin with a brief description of the strategies for material synthesis. There are some novel strategies for device optimization highlighted in this review that enables us to achieve enhanced device performance compared with the conventional methods which tends to be limited to specific device and cannot be applied universally. And then some operation mechanism of the NIRPDs will be extensively probed into. In the final section, the possible challenges and opportunities in the future development of NIRPDs will be briefly proposed. 2. IV Group Semiconductors 2.1. Si Si has an indirect narrow band gap ( 1.12 ev) and is the second most abundant element on the earth. 1D SiNW can be synthesized on large scale by CVD and oxide-assisted growth. [25,26] Moreover, some low-temperature methods such as HF etching are also valid alternatives because they can address most of the limitations of bottom-up synthetic methods. Lieber s group reported the first avalanche photodetectors (APD)-based nanoscale p i n junction Si nanowire (SiNW). [27] The as-formed axial modulation-doped p-i-n SiNW exhibited an avalanche breakdown mechanism with large reverse bias. In addition, the single p i n SiNW could function as an avalanche photodiode: the p-type and n-type regions have multiplication factors of 100 and 20, respectively, comparable to planar Si APDs. By recombining SiNW with graphene oxide, [28] metal films (e.g., Cu, [29] Ag, [30] and Au/Cr [31] ) and other semiconductor NSs including carbon quantum dots, [32] CdTe NRs, [33] a number of Schottky junction NIR photodiodes, and nano-heterojunction NIRPDs have been developed. For example, our group developed a Feng-Xia Liang, received her B.S. degree from Liaocheng University, M.S. degree from University of Science and Technology of China, and Ph.D. degree from City University of Hong Kong, in 2003, 2006 and 2012, respectively. She is currently an associate professor in the School of Materials Science and Engineering at Hefei University of Technology. Her research interest includes the synthesis of low-dimensional semiconductor nanostructures for chemical, biological and optoelectronic devices applications. Jiu-Zhen Wang is currently a graduate student under supervision of Dr. Fengxia Liang in School of Materials Science and Engineering, Hefei University of Technology. He received his BS in Materials Science and Engineering from Liaocheng University in 2014. His current research interest is mainly focused on the fabrication of one-dimensional metal oxide semiconductor nanostructures for ultraviolet photodetector device application. Lin-Bao Luo is a full professor of applied physics at Hefei University of Technology. He received his M.Sc. in inorganic chemistry at the Department of Chemistry, University of Science and Technology of China, and Ph.D. degree in 2009 from the Department of Physics and Materials Sciences, City University of Hong Kong. He joined the Hefei University of Technology in 2011. His research interest mainly focuses on the controlled fabrication of one-dimensional semiconductor nanostructures for optoelectronic and electronic devices applications including photovoltaic devices, photodetector, and nonvolatile memory device. radical SiNW-carbon quantum dots core shell heterojunction for NIR photodetection. [25] The high-quality heterojunction with a barrier height of 0.75 ev exhibited typical rectifying behavior with a rectification ratio as high as 10 3. Thanks to the improved optical absorption and optimized carrier transfer and collection 1700081 (2 of 14)
Table 1. 1D inorganic semiconductor nanostructures-based NIRPDs. Materials Device geometry Wavelength On/off τ r /τ f Detecivity Ref. SiNW Schottky junction 860 nm 300/480 µs [27] SiNW Schottky junction 1064 nm 11.27 70 / ms [29] SiNW Schottky junction 980 nm 1.8 10 4 3.6/14.2 µs 2.9 10 12 [30] SiNW Schottky junction 850 nm 10 7 181/233 ns 7.94 10 12 [39] n-si Schottky junction 890 nm 10 7 0.32/0.75 ms 5.77 10 13 [40] SiNW Schottky junction 850 nm 10 6 73/96 ms 10 14 [41] Ge Schottky junction 1550 nm 2 10 4 23/108 µs 1.38 10 10 [48] GeNN Schottky junction 1550 nm 5 10 4 450/460 ns 2.28 10 13 [49] CNT p n junction 850 nm 7.5/8.8 s [50] CNT Schottky junction 785 nm / 1.09 10 7 [55] CNT Schottky junction 980 nm 2.4 10 2 68/78 µs 4.87 10 10 [57] InP Schottky junction 980 nm 1 411/433 ns 1.05 10 10 [62] InPNW Schottky junction 830 nm 10 29.1/139.6 ms 9.1 10 15 [68] InPNW Schottky junction 2000 nm 24 80/61 us 10 12 [77] InAsNW Schottky junction 1000 nm 10 4 / [79] GaAs Schottky junction 850 nm 7.7 10 2 320/380 ns 7.3 10 9 [87] GaAsNCs Schottky junction 850 nm 10 5 72/122 µs 1.83 10 11 [88] GaSb/GaInSb p n junction 1550 nm 2/3.7 ms [93] GaSbNW photoconductive 700 nm 10 5 80/90 ms 9.67 10 9 [94] Bi 2 S 3 NW photoconductive 1064 nm 5 10 2 0.55/0.4 s 7.5 10 9 [105] Bi 2 S 3 NW photoconductive 808 nm 45/47 ms 2.38 10 12 [106] CdTe NR photoconductive 800 nm 3 1.1/3.3 s [111] CdTe NW Schottky junction 800 nm 6.12/7.53 s 1.25 10 12 [113] capability, we achieved a core shell nano-heterojunction with power conversion efficiency (PCE) as high as 9.1%. In addition, the heterojunction displayed good sensitivity to light illumination with high photosensitivity (10 3 ) and fast response rate (tens of µs). Another strategy to achieve high-performance NIRPD is to simply coat the SiNWs array with high-quality graphene. [34,35] This two-dimensional layered material offers exceptionally high mobility, conductivity, and flexibility. [36,37] The resulting graphene-silicon heterojunction can take the complementary advantages of both materials leading to optimized device performance in terms of high sensitivity, good specific detectivity and fast response speed. [38] Li et al. reported a graphene-n-si heterojunction photodetector for NIR detection. By incorporating an ultrathin interfacial layer into the device structure, the dark current of the graphene/n-si heterojunction was reduced by two orders of magnitude. [39] Notably, after interfacial engineering, the NIRPD had a specific detectivity as high as 5.77 10 13 Jones the highest value among all reported planar graphene/si heterojunction photodetectors. By further engineering the light absorption through light trapping and surface plasmon resonance techniques, we recently developed a highly sensitive NIRPD by modifying free-standing SiNWs arrays with plasmonic gold nanoparticle (AuNP)-decorated graphene layer (Figure 1). This device showed excellent sensitivity to 850 nm illumination with an on/off ratio as high as 10 6. The responsivity and specific detectivity were estimated to be 1.5 AW 1 and 2.52 10 14 Jones, respectively. Finite element method (FEM) modeling showed that this relatively high sensitivity was associated with the strong light trapping of the SiNWs and remarkable surface plasmon resonance (SPR)-induced field enhancement. [40] 2.2. Ge Due to the rapid shrinkage in size of the microelectronic circuitry, on-chip optical interconnection is a competitive substitute for existing electrical interconnects. [41] This technological change entails the development of ultra-compact and siliconcompatible optoelectronic devices. Ge NIRPD plays an important part as the interface between photonics and electronics due to its high mobility, large absorption coefficient in NIR region, and excellent compatibility with the conventional siliconprocessing technology. [42,43] While a number of NIRPD-based GeNWs nanostructures have been fabricated, most devices suffer from a very low responsivity because of the diffraction limit of the light. To eliminate this dilemma, Tang et al. reported a GeNW NIRPD with an active volume on the order of 10 4 λ 3 by exploiting the idea of a half-wave Hertz dipole antenna from 1310 1480 nm. [44] This specially designed device geometry 1700081 (3 of 14)
Figure 1. Step-wise process for the fabrication of the NIRPD, photoresponse of the core shell SiNWs array-cqd heterojunction device, energy band diagram of the heterojunction. Reproduced with permission. [41] Copyright 2014, Nature Publishing Group. had good light trapping effect, which was highly beneficial for photosensing. Further analysis revealed that the photo current was increased 20-fold due to the antenna resonance. Moreover, the NIRPD showed a fast response speed and low capacitance, which rendered it potentially promising for future high-speed, low-power consumption optoelectronic devices. Inspired by this technology, Brongersma s group demonstrated a leak-mode resonance (LMR)-induced field enhancement strategy to tune the spectral absorption features of individual GeNW-based NIRPD (Figure 2). The LMR could confine light in the sub-wavelength regime via high-refractive-index semiconductor nanostructures. Thus, they could enhance and spectrally engineer light absorption. Experimental results revealed that leaky-mode resonance induced field enhancement inside the NS controlled via the sub-wavelength size, geometry and orientation of the NS could enhance and better match the absorption of the broadband spectrum including NIR. [45] Ray and co-workers reported an NIRPD based on Ge/CdS core shell nano-heterojunctions that possessed a relatively large surface-to-volume ratio with carrier occurring in the radical direction. [46] An enhanced photoresponse with broad spectral bandwidth was observed in the core shell NW devices. Our group has recently developed a highly sensitive self-driven MLG-Ge Schottky junction for NIR detection by combining high quality graphene films. Due to the photovoltaic characteristics of the Schottky junction, the NIR device exhibited obvious sensitivity to 1550 nm illumination with an on/off ratio as high as 2 10 4 at zero bias voltage. In addition, it could detect high frequency optical signals with a response speed as fast as 23 µs. [47] Considering the strong reflectance of the planar Ge wafer which is harmful to the photon-to-electron conversion process, we then tried to optimize the light absorption using 1D Ge nanoneedles (GeNNs) array with strong light trapping effect, and plasmonic heavily doped indium tin oxide nanoparticles (ITONPs) that were able to induce localized SPR. [48] Both experimental and simulated results confirmed that the as-fabricated plasmonic NIRPD exhibited enhanced light absorption in NIR. 1700081 (4 of 14)
Figure 2. Schematic illustration of single GeNW PD, SEM image of a GeNW device, and measured spectra of absorption efficiency Q abs for unpolarized light including correlation of the absorption curve in GeNW with leaky-mode resonances (LMR). Reproduced with permission. [46] Copyright 2009, Nature Publishing Group. Optoelectronic characterization revealed that the ITONP-modified NIRPD exhibited high sensitivity to 1550 nm illumination under zero bias with a very quick response. The on/off ratio, responsivity, and specific detectivity were 5 10 4, 185 ma/w and 2.28 10 13 cm Hz 1/2 W 1, respectively, which were much better than that without ITONPs. 2.3. CNT CNTs are an equally important candidate for NIRPDs applications because of their unique photoelectric and chemical properties such as direct structure-dependent band gap, low heat capacity, unique 1D van Hove singularities, and broadband optical absorption in the NIR regime. [49 51] To date, various synthetic methods including laser ablation, chemical vapor deposition (CVD) and pyrolyzing metal carbonyls have been successfully developed to fabricate semiconducting CNTs ever since the first observation of a CNT in 1991. [52] Avouris et al. from IBM developed the first single CNT NIRPD by incorporating laser ablation-derived single CNTs as the channel of an ambipolar field-effect transistor (FET), [53] which could function as a polarized NIR (780 and 980 nm) photodetector with an estimated quantum efficiency of 10%. In addition to a single CNT, NIR radiation can also be reliably detected with devices composed of horizontally aligned CNT arrays (Figure 3). [54,55] The efficient exciton dissociation is vitally important for a high photonics response. [56] Wu s group reported an NIRPD composed of graphene-cnts nanohybrids with a novel exciton dissociation mechanism. Such a heterojunction demonstrated enhanced exciton dissociation at the graphene-cnts interfaces leading to enhanced photoconductivity. The photoresponsivity to NIR illumination (1 1.3 µm) was enhanced by one order of magnitude. The specific detectivity was as high as 1.5 10 7 Jones, which is a 5-fold improvement over the best value achieved on other CNT film devices. [57] This group later found that the CNTs-P 3 HT interface had an efficient exciton dissociation capability as well. They then developed a CNT-polymer type-ii heterojunction NIR detector that could efficiently dissociate excitons through an intrinsic energy offset via the CNT-P 3 HT band alignment. [58] In this case, the specific detectivity was as high as 2.3 10 8 cm Hz 1/2 W comparable to that of other uncooled NIRPDs. 3. III-V Group Semiconductors 3.1. InP InP with a direct band gap of 1.34 ev is of both scientific and technological significance due to its high carrier mobility and efficient luminescence property. [59 61] The 1D InP NSs such as NW and NR have shown potential applications in light detecting devices. [62,63] Pettersson and coworkers reported an efficient NIRPD based on vertically aligned i-n + InP NW grown on a p + InP wafer. Device analysis revealed that the NIRPD exhibited 1700081 (5 of 14)
Figure 3. Schematic illustration of fabrication the photodiode, microscopy image of CNT array diode with channel length L = 1 µm, I V curves of the CNTs diode measured with and without NIR illuminations, experimental and fitted results for open circuit voltage, and short circuit current as a function of NIR density. Bottom right panel shows photoresponse of the CNT photodetector under varied densities. Reproduced with permission. [55] Copyright 2012, Optical Society of America. obvious rectifying characteristics with an ideality factor of 2.5 at room temperature and relatively small leakage current at low reverse bias (100 fa/nw@1v). Furthermore, there was a linear increase in the photocurrent with reverse bias up to about 10pA/NW at 5 V. [64] According to their spectrally resolved characterization, the photocurrent collection process depends strongly on the p + -segment length. [65] By controllably doping the InP NW with As atoms via a two-step growth route, Pan s group successfully obtained InAs x P 1 x NWs with complete compositional tunability. They observed that the ternary compound NIRPD showed a band-selective infrared sensitivity: when the x value increased, the photocurrent red-shifted from ca. 900 cm to ca. 2900 nm. Meanwhile, the InAs x P 1 x NW devices all have higher responsivity and quantum efficiency than their binary NW counterparts. [66] For the majority of the NIRPDs assembled from 1D semiconductor nanostructures, one particular challenge for further application is low dark current, which is beneficial for both responsivity and detectivity. To solve this problem, Hu s group recently proposed a simple and efficient technology to suppress the dark current of the NW NIRPD. [67,68] They intentionally deposited a layer of ferroelectrinc polymer (VDF-TrFE) on the surface of the InAs NW device (Figure 4). With positive or negative direction of the remnant polarization electrostatic field, the InAs NW channel could be maintained in a fully depleted or accumulated state. As a result, the dark current was substantially reduced, giving rise to a very high photoconductive gain, responsivity and specific detectivity of 4.2 10 5, 2.8 10 5 A W 1, and 9.1 10 15 Jones, respectively. 3.2. InAs With a high mobility and a very small bandgap (0.35 ev), 1D InAs NWs are suitable for applications in high-speed electronic components and broad-spectrum detection. [69,70] To date, two different photosensing mechanisms have been identified on InAs NWs NIRPD: one is a positive response and the other is a negative photoresponse which is believed to be related to the effect of surface states. [71,72] Based on singlecrystal InAs NWs synthesized by CVD or molecular beam epitaxy (MBE) methods, [73,74] several groups successfully fabricated single InAs NW NIRPDs with an obvious positive response. 1700081 (6 of 14)
Figure 4. Schematic illustration of the ferroelectric side-gated InP NW detector, photoresponse of the ferroelectric side-gated individual InP NW based photodetector, photoresponsivity and detectivity of the InP NW photodetector under various intensities, and the mechanism of the different ferroelectric polarization states. Reproduced with permission. [68] Copyright 2016, American Chemical Society. Hu et al. reported an InAs NW NIR phototransistor with a high photoconductive gain of 10 5 and a fast response speed of 12 ms. [75] This relatively high performance was related to the trapping mechanism of the near surface photogating layer that leads to strong photogating effect on the NW channel by capturing photogenerated carriers. To reduce the dark current and enhance the infrared sensitivity of a single InAs NW photodetector, this group later proposed a novel visible light-assisted dark-current suppressing technology (Figure 5). [76] This strategy could effectively increase the barrier height of the metal-semiconductor contact, leading to the formation of a metal-semiconductor-metal photodiode that exhibits broad detection from less than 1 to more than 3 micrometers. Optoelectronic analysis revealed that this technique could not only increase the responsivity and detectivity, but also extend the detection waveband. The integration of high-quality InAs NW with Si or graphene is of great interest for NIRPDs as well. [77,78] For example, Liao et al. fabricated a graphene-inas NW heterojunction NIRPD that had a maximum on/off ratio of 5 10 2, which is much larger than that of a single InAs NW device. In addition, the responsivity was 5 10 3 times larger than that of graphene NIRPD. 3.3. GaAs Unlike Si, the chemical composition and band gap of GaAs can be readily tuned to better match the solar spectrum. [79] Therefore, GaAs particularly GaAs NW is the material of choice for high-efficiency solar cells. They have the highest power conversion efficiency at 20%, which is very close to the theoretical value. [80,81] Another equally important application is NIRPD. Wang et al. developed an individual undoped GaAs NW NIRPD with a MSM Schottky junction geometry. The photoconductive gain of the photodetector was as high as 2 10 4 at relatively low NIR excitation. Further spectral response and numerical simulation revealed that this high gain was associated with a band-edge absorption profile and leaky-mode resonance. Using conductive atomic force microscopy, Hu s group found that the optoelectronic property of individual GaAs NW-based photodetectors were dependent on the doping level. [82] They systematically studied the photoresponse of individual GaAs NW with various doping levels and concluded that in contrast to doped NWs, the photocurrent of NW with doping concentrations higher than 2 10 17 cm 3 displayed an abnormal linear relationship against the reverse bias voltage of the tip-nw Schottky junction. This suggests that n-type doping can sharply decrease the NW carrier lifetime. Recently, Seyedi and co-workers presented a GaAs NW/ indium-tin-oxide Schottky-like heterojunction photodetector for 850 nm detection this is technologically important for date communication systems. [83] The GaAs device architecture allowed the active detection area to be distributed over a large area which leads to a large detection area with low capacitance. Further device analysis showed that the NW device could 1700081 (7 of 14)
Figure 5. Operation mechanism of the InAs NW photodetector and photoresponse analysis of the InAs NW-based NIRPDs. Reproduced with permission. [77] Copyright 2014, Wiley-VCH. achieve 0.5 A W 1 with a signal-noise ratio as large as 7 db. Furthermore, the capacitance-voltage was estimated to be less than 5 nf cm 2, which showed strong potential for integration into high-speed optoelectronic devices (Figure 6). [84] By recombining the GaAs with high quality graphene, it is also possible to achieve highly sensitive NIRPDs. Various studies have shown that the as-fabricated graphene-gaas NIRPD has a fast response speed and relatively low energy consumption thanks to the formation of built-in electric fields. [85,86] For instance, our group recently reported a monolayer graphene-n-type GaAs nanocones (GaAsNCs) array Schottky junction for NIR light detection. [87] The GaAsNCs array was synthesized via a metal-assisted chemical etching approach. Device analysis showed that the NIRPD had high sensitivity to 850 nm with a high response speed (rise time: 72 µs, fall time: 122 µs); The on-off ratio was as high as 10 4. Furthermore, the detectivity was determined to be 1.83 10 11 cm Hz 1/2 W 1, which is higher than the other GaAs-based devices. 3.4. GaSb As a typical p-type semiconductor, the 1D GaSb NSs has been the focus of increasing interest for their applications as single hole transistors in spintronics and high-performance electronic devices. [88,89] Recently, single crystal GaAs and GaSbbased alloy NWs have been successfully fabricated through various methods including metal/organic vapor phase exitaxy (MOVPE) and the CVD method. [90,91] Due to their wide range of band gaps, the GaSb NSs have been used in high-speed optoelectronic devices in the infrared region. Pan et al. reported an ultrasensitive NIRPD based on GaSb/GaInSb p-n heterojunction NWs (Figure 7) via CVD. [92] Such a heterojunction photodiode was photoresponsive in the infrared communication region with an EQE of 10 4, a responsivity of 10 3 A W 1, and a short response speed of 2 milliseconds. Another highly sensitive NIRPD was constructed on individual GaSb NW by Shen s group. [93] The GaSb NW device demonstrated very good responsivity, fast response speed, and long-term ambient stability. Moreover, the GaSb NW can be also constructed on a flexible and transparent polyethylene terephthalate (PET) substrate. Excellent optoelectronic characteristics were observed for the flexible device under different bending stages and bending cycles. 4. Chalcogenide Semiconductors 4.1. Sulfide Although nanostructures for NIRPD applications were dominated by both the IV group and III-VI group semiconductors, other compound semiconductors including chalcogenides (e.g., sulfide, selenide, and telluride) should not be neglected. The 1D Bi 2 S 3 NSs with various morphologies have been synthesized through various methods such as a hydrothermal, [94 96] solvothermal, [97,98] molten salt solvent, [99] and solution refluxing methods. [100,101] Andzane et al. developed a novel Bi 2 S 3 NW photodetector that was sensitive to both visible and NIR light radiation. The Bi 2 S 3 NWs array was grown within an anodized alumina membrane, and this significantly influenced the photoconductive properties of the anodic aluminum oxide 1700081 (8 of 14)
Figure 6. Schematic illustration of transparent top contact, and AlGaAs/GaAs shell/core NW array, SEM image of the passivated NW array after growth, SEM image of the NW array infiltrated with polymer, and photocurrent of NW array device under different intensities. Reproduced with permission. [85] Copyright 2013, American Institute of Physics. (AAO)-hosted Bi 2 S 3 NW. The individual Bi 2 S 3 NW device showed a fast and pronounced photoresponse under low-power radiation, while the AAO-hosted NWs array displayed a relatively slow increase in photocurrent. More recently, we proposed a feasible approach for high-performance NIRPD by introducing plasmonic hollow gold nanoparticles (HGNs) with a strong LSPR onto the surface of Bi 2 S 3 NS. [102] The photosensitivity of the plasmonic photodetectors was considerably enhanced after decoration with HGNs. Furthermore, the responsivity increased from 1.4 10 2 to 1.09 10 3 AW 1, and the photoconductivity gain increased from 2.68 10 2 to 2.31 10 3. The specific detectivity increased from 2.45 10 12 to 2.78 10 13 cm Hz 1/2 W 1, respectively. This optimization in sensitivity was attributed to the LSPR effect caused by the HGNs according to both experiment and theoretical simulation based on FEM. 4.2. Selenide Bi 2 Se 3 has been widely used as a platform for strong topological insulators and has a topologically narrow bulk band gap at 0.35 ev. Bi 2 Se 3 NW is a new type of quantum matter that is prepared from a thermal evaporation method. It has aroused great research interest in the fabrication of novel dissipationless PDs due to its unique properties and nontrivial Dirac carriers that are insulated in the bulk but are conductive on the surface. [103] For example, Sharma et al. reported an NIRPD based on the topological insulators of single Bi 2 Se 3 NW. [104] They observed efficient electron hole pair generation in the NW under IR light illumination. The responsivity was estimated to be 300 A W 1, which was four orders of magnitude larger than other devices with similar geometry. Recently, Jie s group developed a Bi 2 Se 3 NW/Si heterojunction photodetector with ultrahigh responsivity and broadband response (Figure 8). [105] A Schttoky junction was formed at the Si/topological insulator contact due to the unique band diagram of the Bi 2 Se 3 NWs with an n-type bulk state and a topological metallic surface states. When irradiated by incident light, electron-hole pairs were generated in the NWs because of the transition of electrons from the bulk valence band to the empty bulk conduction band. The electron-hole pairs were then swiftly separated by the electric field, leading to photocurrent in the circuit. The photodetectors exhibited excellent detection capability with an optimized responsivity of 10 3 A W 1 and a broad spectral region from 380 to 1310 nm. This responsivity was the highest value for the photodetectors based on topological insulator. 4.3. Telluride As a group II-VI semiconductor material, CdTe is a promising candidate for solar cell applications due to its high theoretical 1700081 (9 of 14)
Figure 7. SEM image of the as-fabricated GaSb/Ga 0.9 In 0.1 Sb nanojunction, real-color image of the nano-heterojunction on a Si wafer, I V characteristics of the GaSb/Ga 0.9 In 0.1 Sb nano-heterostructure under light illumination with different wavelengths, the wavelength selected photoresponse of the nano-photodetector, the photocurrent as a function of incident power intensity, and the reproducible switching between on and off states under 1550 nm illumination. Reproduced with permission. [93] Copyright 2014, American Chemical Society. power conversion efficiency (30%), which is higher than Si. [106] In addition, CdTe particularly 1D CdTe NSs have applications in NIR light detection. [107 109] Zhang et al. developed a sensitive NIR photodetector made of CdTe nanoribbons with typical p-type conductivity. [110] The nanostructured device has a significant photoresponse to NIR irradiation with a responsivity as high as 7.8 10 2 A/W. It also demonstrated high stability and reliability. Similarly, photodetector based on CdTe NW device also displayed photo-conductive characteristic. [111] In comparison with the CdTe NR, the CdTe NW device had a relatively low responsivity (19.2 A W 1 ) and photoconductive gain (250). To optimize the sensitivity of CdTe NSs-based photodetectors, we decorated plasmonic AuNPs on the surface of the CdTe NW (Figure 8). [112] The resulting plasmonic NIRPD witnessed a considerable increase in photocurrent. This gives rise to obvious improvements in responsivity and specific detectivity. Specifically, the responsivity, photoconductivity gain, and specific detectivity were estimated to be 2.26 10 4 A/W, 3.51 10 4, and 1.25 10 12 Jones, respectively. These are much better that other CdTe nanostructure-based devices. In light of theoretical simulation based on finite-difference time-domain (FDTD) method, the observed optimization in sensitivity was attributed to the surface plasmon resonance effect of AuNPs. In 2 Te 3 with a band-gap of around 1.1 ev is suitable for NIR photodetection due to its suppressed thermally excited carriers and relatively large photo-to-current ratio. It is an ideal alternative candidate for post-silicon optoelectronic devices because of its excellent ambient stability and high absorption coefficients as large as 1 10 5 cm 1. This is several times larger than that of Si. [113] The 1D In 2 Te 3 NW exhibited enhanced and physical properties in thermoelectric, sensing, and optoelectronic device applications. [114] He s group reported the first sensitive In 2 Te 3 NW NIRPD. [115] Spectral analysis revealed that the as-assembled device had a broadband photoresponse with peak responsivity at 800 nm. Specifically, the photodetector has an EQE as high as 60%. Later, Yan et al. found that the In 2 Te 3 NW or NT synthesized through a simple solvothermal approach can be used to fabricate NIR photodetectors with good sensitivity and reproducibility. [116,117] It also revealed that photodetectors based on individual In 2 Te 3 NTs have a broad spectral detection range from 300 1100 nm, which is very close to that of In 2 Te 3 NW. 5. Conclusion and Outlook In this article, we briefly reviewed recent research progress in the field of near infrared light photodetectors based on onedimensional inorganic semiconductor NSs, which are versatile building blocks due to their excellent optoelectronic properties. Various narrow band-gap elementary semiconductors (e.g., Si, Ge, and CNTs) and binary compound semiconductor (III-VI and chalcogenides) in the form of nanowires, nanorods, nanoribbons, and nanotubes have been fabricated by both top-down and bottom-up approaches. Based on these one-dimensional NSs, a host of near infrared light photodetectors with device geometries ranging from photoconductive-type detectors, metal-semiconductor Schottky junction detectors, to nanoheterojunction detectors have been developed. Comparatively, the near infrared light photodetectors based on single InP NW exhibited the highest specific detectivity (9.1 10 15 Jones). In 1700081 (10 of 14)
Figure 8. Schematic illustration of heterojunction device, SEM image of the photodetector, I-V characteristics of the heterojunction in the dark and under light illumination, photoresponse of the device under 808 nm light, the response speed analysis of the device. Reproduced with permission. [106] Copyright 2016, Royal Society of Chemistry. addition, the graphene/si NW Schottky junction near infrared light photodetector had an on/off ratio of 10 7 and a nanosecond response speed (τ rise /τ fall : 181:233 ns), which is the best response speed ever reported. These excellent device performance features confirm that one-dimensional inorganic semiconductor nanostructure-based near infrared light photodetectors support the high expectations and promises of these novel materials. Despite this progress, the near infrared light photodetectors are still limited by some problems that need to be addressed. First, the synthesis of novel inorganic semiconductor NSs with superb optoelectronic properties remains challenging. The optoelectronic characteristics of one-dimensional semiconductor NSs are largely determined by their morphology, chemical composition, doping level, and orientation. Even though great efforts have been devoted to fabricating various onedimensional nanostructures, precise control of the one-dimensional nanomaterials with highly uniform geometry, structure, and doping is still lacking. This is the main bottleneck to future widespread applications. Strategies, which are simple, low-cost, and highly reproducible for synthesizing versatile one-dimensional nanostructures should be urgently developed. Second, the integration of prototype near infrared light photodetectors requires greater functionalities. To date, various single near infrared light photodetector prototypes have been reported, and these devices are superior in various device parameters when compared to their thin film and bulk counterparts. Nevertheless, it is inevitable to note that their reproducibility varies considerably from one device to another. To address this problem, it is necessary to fabricate and integrate single near infrared light photodetectors into functional devices on a large scale. Furthermore, the ability to reliably manipulate and assemble individual one-dimensional semiconductor nanostructures at specific areas with desired density and alignments during device fabrication has yet to be developed. Third, although some simulation methods such as Finite-Difference Time-Domain and Finite Element Method are employed to optimize the optical management, there is relatively little 1700081 (11 of 14)
work focusing on theoretical analysis including a detailed process for transforming photons to electricity this is fundamentally important from the perspective device performance optimization. Acknowledgement This work was supported by the Natural Science Foundation of China (NSFC, Nos. 21501038, 61575059, 61675062), the Natural Science Foundation of Anhui Province of China (Nos. 1408085MB31, J2014AKZR0036), the China Postdoctoral Science Foundation (103471013), and the Fundamental Research Funds for the Central Universities (Nos. 2013HGXJ0195, 2013HGCH0012, 2014HGCH0005). Conflict of Interest The authors declare no conflict of interest. Keywords compound semiconductors, near-infrared light, one-dimensional semiconductor nanostructures, optoelectronic devices, photodetectors Received: January 25, 2017 Revised: April 8, 2017 Published online: [1] J. Qi, W. Qiao, Z. Y. Wang, Chem. Rec. 2016, 16, 1531. [2] C. Downs, T. E. Vandervelde, Sensors 2013, 13, 5054. [3] L. S. Li, Y. Y. Huang, J. B. Peng, Y. Cao, X. B. Peng, J. Mater. Chem. C 2014, 2, 1372. [4] C. Daffara, E. Pampaloni, L. Pezzati, B. Barucci, R. Fontana, Accounts Chem. Res. 2010, 43, 847. [5] W. T. Lai, P. H. Liao, A. P. Homyk, A. Scherer, P. W. Li, IEEE Photonics Technol. Lett. 2013, 25, 1520. [6] L. L. Gu, M. M. Tavakoli, D. Q. Zhang, Q. P. Zhang, A. Waleed, Y. Q. Xiao, K. H. Tsui, Y. J. Lin, L. Liao, J. N. Wang, Z. Y. Fan, Adv. Mater. 2016, 28, 9713. [7] H. B. Zhang, X. J. Zhang, C. Liu, S. T. Lee, J. S. Jie, ACS Nano 2016, 10, 5113. [8] Z. X. Wang, M. Safdar, C. Jiang, J. He, Nano Lett. 2012, 12, 4715. [9] L. Li, W. K. Wang, L. Gan, N. Zhou, X. D. Zhu, Q. Zhang, H. Q. Li, M. L. Tian, T. Y. Zhai, Adv. Funct. Mater. 2016, 26, 8281. [10] H. Huang, J. L. Wang, W. D. Hu, L. Liao, P. Wang, X. D. Wang, F. Gong, Y. Chen, G. J. Wu, W. J. Luo, X. S. Chen, J. H. Chu, Nanotechnology 2016, 27, 445201. [11] S. F. Leung, Q. P. Zhang, F. Xiu, D. L. Yu, J. C. Ho, D. D. Li, Z. Y. Fan, J. Phys. Chem. Lett. 2014, 5, 1479. [12] J. S Jie, W. J. Zhang, Y. Jiang, X. M. Meng, Y. Q. Li, S. T. Lee, Nano Lett. 2006, 6, 1887. [13] S. D. Lim, D. S. Um, M. J. Ha, Q. P. Zhang, Y. S. Lee, Y. J. Lin, Z. Y. Fan, H. H. Ko, Nano Res. 2017, 10, 22. [14] H. Y. Chen, H. Liu, Z. M. Zhang, K. Hu, X. S. Fang, Adv. Mater. 2016, 28, 403. [15] J. S. Jie, W. J. Zhang, I. Bello, C. S. Lee, S. T. Lee, Nano Today 2010, 5, 313. [16] C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo, Nano Lett. 2007, 7, 1003. [17] X. Liu, X. Liu, J. Wang, C. Liao, X. Xiao, S. Guo, C. Jiang, Z. Fan, T. Wang, X. Chen, W. Lu, W. Hu, L. Liao, Adv. Mater. 2014, 26, 7399. [18] G. J. Wu, X. D. Wang, P. Wang, H. Huang, Y. Chen, S. Sun, H. Shen, T. Lin, J. L. Wang, S. T. Zhang, L. F. Bian, J. L. Sun, X. J. Meng, J. H. Chu, Nanotechnology 2016, 27, 364002. [19] L. Wang, J. S. Jie, Z. B. Shao, Q. Zhang, X. H. Zhang, Y. M. Wang, Z. Sun, S. T. Lee, Adv Funct. Mater. 2015, 25, 2910. [20] G. Chen, B. Liang, X. Liu, Z. Liu, G. Yu, X. M. Xie, T. Luo, M. Q. Zhu, G. Z. Shen, Z. Y. Fan, ACS Nano 2014, 8, 787. [21] Q. S. Wang, J. Li, Y. Wen, Z. X. Wen, Z. X. Wang, X. Y. Zhan, F. Wang, F. M. Wang, Y. Huang, K. Xu, J. He, Adv. Mater. 2016, 28, 3596. [22] X. Xia, T. X. Li, H. J. Tang, L. Zhu, X. Li, H. M. Gong, W. Lu, Sci. Rep. 2016, 6, 21544. [23] L. Peng, L. F. Hu, X. S. Fang, Adv. Mater. 2013, 25, 5321. [24] X. Q. Liu, X. Liu, J. L. Wang, C. N. Liao, X. H. Xiao, S. S. Guo, C. Z. Jiang, Z. Y. Fan, T. Wang, X. S. Chen, W. Lu, W. D. Hu, L. Liao, Nanotechnology 2014, 26, 7399. [25] V. Schmidt, J. V. Wittemann, S. Senz, U. Gosele, Adv. Mater. 2009, 21, 2681. [26] S. Das, V. Dhyani, Y. M. Georgiev, D. A. Williams, Appl. Phys. Lett. 2016, 108, 063113. [27] C. Yang, C. J. Barrelet, F. Capasso, C. M. Lieber, Nano Lett. 2006, 6, 2929. [28] Y. Cao, J. Y. Zhu, J. Xu, J. H. He, J. L. Sun, Y. X. Wang, Z. R. Zhao, Small 2014, 10, 2345. [29] C. Y. Wu, Z. Q. Pan, Y. Y. Wang, C. W. Ge, Y. Q. Yu, J. Y. Xu, L. Wang, L. B. Luo, J. Mater. Chem. C 2016, 4, 10804. [30] E. Mulazimoglu, S. Coskun, M. Gunoven, B. Butun, E. Ozbay, R. Turan, H. E. Unalan, Appl. Phys. Lett. 2013, 103, 083114. [31] K. Das, S. Mukherjee, S. Manna, A. K. Raychaudhuri, Nanoscale 2014, 6, 11232. [32] C. Xie, B. Nie, L. H. Zeng, F. X. Liang, M. Z. Wang, L. B. Luo, M. Feng, Y. Q. Yu, C. Y. Wu, Y. C. Wu, S. H. Yu, ACS Nano 2014, 8, 4015. [33] C. Xie, L. B. Luo, L. H. Zeng, L. Zhu, J. J. Chen, B. Nie, J. G. Hu, Q. Li, C. Y. Wu, L. Wang, CrystEngComm 2012, 14, 7222. [34] Y. M. Wang, K. Ding, B. Q. Sun, S. T. Lee, J. S. Jie, Nano Res. 2016, 9, 72. [35] C. Xie, P. Lv, B. Nie, J. Jie, X. Zhang, Z. Wang, P. Jiang, Z. Z. Hu, L. B. Luo, Z. F. Zhu, L. Wang, C. Y. Wu, Appl. Phys. Lett. 2011, 99, 133113. [36] C. Xie, J. S. Jie, B. Nie, T. X. Yan, Q. Li, P. Lv, F. Z. Li, M. Z. Wang, C. Y. Wu, L. Wang, L. B. Luo, Appl. Phys. Lett. 2011, 100, 193103. [37] W. Y. Kong, G. A. Wu, K. Y. Wang, F. T. Zhang, Y. F. Zou, D. D. Wang, L. B. Luo, Adv. Mater. 2016, 28, 10725. [38] F. X. Liang, D. Y. Zhang, Y. Zou, H. Hu, T. F. Zhang, Y. C. Wu, L. B. Luo, RSC Adv. 2015, 5, 19020. [39] X. M. Li, M. Zhu, M. D. Du, Z. Lv, Z. L Zhang, Y. C. Li, Y. Yang, T. T. Yang, X. Li, K. L. Wang, H. W. Zhu, Y. Fang, Small 2016, 12, 595. [40] L. B. Luo, L. H. Zeng, C. Xie, Y. Q. Yu, F. X. Liang, C. Y. Wu, L. Wang, J. G. Hu, Sci. Rep. 2014, 4, 3914. [41] L. Y. Cao, J. S. Park, P. Y. Fan, B. Clemens, M. L. Brongersma, Nano Lett. 2010, 10, 1229. [42] H. S. Lee, C. J. Kim, D. Lee, R. R. Lee, K. Kang, I. Hwang, M. H. Jo, Nano Lett. 2012, 12, 5913. [43] J. Greil, A. Lugstein, C. Zeiner, G. Strasser, E. Bertagnolli, Nano Lett. 2012, 12, 6230. [44] L. Tang, S. E. Kocabas, S. Latif, A. K. Okyay, D.S. Ly-Gagnon, K. C. Saraswat, D. A. B. Miller, Nat. Photonics 2008, 2, 226. [45] L. Cao, J. S. White, J. S. Park, J. A. Schuller, B. M. Clemens, M. L. Brongersma, Nat. Mater. 2009, 8, 643. 1700081 (12 of 14)
[46] S. P. Mondal, S. K. Ray, Appl. Phys. Lett. 2009, 94, 223119. [47] L. H. Zeng, M. Z. Wang, H. Hu, B. Nie, Y. Q. Yu, C. Y. Wu, L. Wang, J. G. Hu, C. Xie, F. X. Liang, L. B. Luo, ACS Appl. Mater. Interfaces 2013, 5, 9362. [48] R. Lu, C. W. Ge, Y. F. Ge, K. Zheng, D. D. Wang, T. F. Zhang, L. B. Luo, Laser Photonics Rev. 2016, 10, 595. [49] Z. L. Huang, M. Gao, Z. C. Yan, T. S. Pan, F. Y. Liao, Y. Lin, Nanoscale 2016, 8, 9593. [50] G. E. Fernandes, Z. Liu, J. H. Kim, C. H. Hsu, M. B. Tzolov, J. Xu, Nanotechnology 2010, 21, 465204. [51] Z. Y. Zhan, C. Liu, L. X. Zheng, G. Z. Sun, B. S. Li, Q. Zhang, Phys. Chem. Chem. Phys. 2011, 13, 20471. [52] D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, M. C. Hersam, Chem. Soc. Rev. 2012, 42, 2824. [53] M. Freitag, Y. Martin, J. A. Misewich, R. Martel, P. Avouris, Nano Lett. 2003, 3, 1067. [54] Q. S. Zeng, S. Wang, L. J. Yang, Z. X. Wang, T. Pei, Z. Y. Zhang, L. M. Peng, W. W. Zhou, J. Liu, W. Y. Zhou, S. S. Xie, Opt. Mater. Express 2012, 2, 839. [55] R. B. Rao, X. Liu, T. Li, Y. X. Zhou, Y. L. Wang, Nanotechnology 2009, 20, 055501. [56] T. F. Zhang, Z. P. Li, J. Z. Wang, W. Y. Kong, G. A. Wu, Y. Z. Zheng, Y. W. Zhao, E. X. Yao, N. X. Zhuang, L. B. Luo, Sci. Rep. 2016, 6, 38569. [57] R. T. Lu, C. Christianson, B. Weintrub, J. Z. Wu, ACS Appl. Mater. Interfaces 2013, 5, 11703. [58] R. T. Lu, C. Christianson, A. Kirkeminde, S. Q. Ren, J. Wu, Nano Lett. 2012, 12, 6244. [59] X. Yan, B. Li, Y. Wu, X. Zhang, X. M. Ren, Appl. Phy. Lett. 2016, 109, 053109. [60] G. Chen, B. Liang, Z. Liu, G. Yu, X. M. Xie, T. Luo, Z. Xie, D. Chen, M. Q. Zhu, G. Z. Shen, J. Mater. Chem. C 2014, 2, 1270. [61] L. B. Luo, Y. F. Zou, C. W. Ge, K. Zheng, D. D. Wang, R. Lu, T. F. Zhang, Y. Q. Yu, Z. Y. Guo, Adv. Opt. Mater. 2016, 4, 763. [62] T. Y. Duan, C. N. Liao, T. Chen, N. Yu, Y. Liu, H. Yin, Z. J. Xiong, M. Q. Zhu, Nano Energy 2015, 15, 293. [63] V. J. Logeeswaran, A. Sarkar, M. S. Islam, N. P. Kobayashi, J. Straznicky, X. M. Li, W. Wu, S. Mathai, M. R. T. Tan, S. Y. Wang, R. S. Williams, Appl. Phys. A 2008, 91, 1. [64] H. Pettersson, I. Zubritskaya, N. T. Nghia, J. Wallentin, M. T. Borgström, K. Storm, L. Landin, P. Wickert, F. Capasso, L. Samuelson, Nanotechnology 2012, 23, 1903. [65] C. Jain, A. Nowzari, J. Wallentin, M. T. Borgstrom, M. E. Messing, D. Asoli, M. Graczyk, B. Witzigmann, F. Capasso, L. Samuelson, H. Petersson, Nano Res. 2014, 7, 544. [66] P. Y. Ren, W. Hu, Q. L. Zhang, X. L. Zhu, X. J. Zhuang, L. Ma, X. P. Fan, H. Zhou, L. Liao, X. F. Duan, A. L. Pan, Adv. Mater. 2014, 26, 7444. [67] D. S. Zhang, J. L. Wang, W. D. Hu, L. Liao, H. H. Fang, N. Guo, P. Wang, F. Gong, X. D. Wang, Z. Y. Fan, X. Wu, X. J. Meng, X. S. Chen, W. Lu, Nano Lett. 2016, 16, 2548. [68] D. S. Zhang, H. H. Fang, P. Wang, W. J. Luo, F. Gong, J. C. Ho, X. S. Chen, W. Lu, L. Liao, J. L. Wang, W. D. Hu, Adv. Funct. Mater. 2016, 26, 7690. [69] J. S. Li, X. Yan, F. K. Sun, X. Zhang, X. M. Ren, Appl. Phys. Lett. 2015, 107, 263103. [70] W. Wei, X. Y. Bao, C. Soci, Y. Ding, Z. L. Wang, D. L. Wang, Nano Lett. 2009, 9, 2926. [71] Y. M. Yang, X. Y. Peng, H. S. Kim, T. H. Kim, S. H. Jeon, K. Kang, W. J. Choi, J. D. Song, Y. J. Doh, D. Yu, Nano Lett. 2015, 15, 5875. [72] Y. X. Han, X. Zheng, M. Q. Fu, D. Pan, X. Li, Y. Guo, J. H. Zhao, Q. Chen, Chem. Phys. Chem. Phys. 2016, 18, 818. [73] J. S. Miao, W. D. Hu, N. Guo, Z. Y. Lu, X. M. Zou, L. Liao, S. X. Shi, P. P. Chen, Z. Y. Fan, J. C. Ho, T. X. Li, X. S. Chen, W. Lu, ACS Nano 2014, 8, 3628. [74] Z. Liu, T. Luo, B. Liang, G. Chen, G. Yu, X. M. Xie, D. Chen, G. Z. Shen, Nano Res. 2013, 6, 775. [75] N. Guo, W. D. Hu, L. Liao, S. Yip, J. C. Ho, J. S. Miao, Z. Zhang, J. Zou, T. Jiang, S. W. Wu, Adv. Mater. 2014, 26, 8203. [76] H. H. Fang, W. D. Hu, P. Wang, N. Guo, W. J. Luo, D. S. Zheng, F. Gong, M. Luo, H. Z. Tian, X. T. Zhang, C. Luo, X. Wu, P. P. Chen, L. Liao, A. L. Pan, X. S. Chen, W. Lu, Nano Lett. 2016, 16, 6416. [77] A. Brenneis, J. Overbeck, J. Treu, S. Hertenberger, S. Morkotter, M. Doblinger, J. J. Finley, G. Abstreiter, G. Koblmuller, A. W. Holleitner, ACS Nano 2015, 9, 9849. [78] J. S. Miao, W. D. Hu, N. Guo, Z. Y. Lu, X. Q. Liu, L. Liao, P. P. Chen, T. Jiang, S. W. Wu, J. C. Ho, L. Wang, X. S. Chen, W. Lu, Small 2015, 11, 936. [79] I. Aberg, G. Vescovi, D. Asoli, U. Naseeem, J. P. Gilboy, C. Sundvall, A. Dahlgren, K. E. Sevensson, N. Anttu, M. T. Bjork, L. Samuelson, IEEE J. Photovoltaics 2016, 6, 185. [80] J. S. Czaban, D. A. Thompson, R. R. Lapierre, Nano Lett. 2009, 9, 148. [81] H. Wang, Appl. Phys. Lett. 2013, 103, 093101. [82] H. Xia, Z. Y. Lu, T. X. Li, P. Parkinson, Z. M. Liao, F. H. Liu, W. Lu, W. D. Hu, P. P. Chen, H. Y. Xu, J. Zou, C. Jagadish, ACS Nano 2012, 6, 6005. [83] M. A. Seyedi, M. Yao, J. O Brien, S. Y. Wang, P. D. Dapkus, Appl. Phys. Lett. 2014, 105, 041105. [84] M. A. Seyedi, M. Yao, J. O Brien, S. Y. Wang, P. D. Dapkus, Appl. Phys. Lett. 2013, 103, 251109. [85] Y. Wu, X. Yan, X. Zhang, Appl. Phys. Lett. 2016, 109, 183101. [86] L. B. Luo, H. Hu, X. H. Wang, R. Lu, Y. F. Zou, Y. Q. Yu, F. X. Liang, J. Mater. Chem. C 2015, 3, 4723. [87] L. B. Luo, J. J. Chen, M. Z. Wang, H. Hu, C. Y. Wu, Q. Li, L. Wang, J. A. Huang, F. X. Liang, Adv. Funct. Mater. 2014, 24, 2794. [88] Z. X. Yang, N. Han, M. Fang, H. Lin, H. Y. Cheung, S. Yip, E. J. Wang, T. Hung, C. Y. Wong, J. C. Ho, Nat. Commun. 2014, 5, 5249. [89] B. Ganjipour, H. A. Nilsson, B. M. Borg, L. W. Wernersson, L. Samuelson, H. Xu, C. Thelander, Appl. Phys. Lett. 2011, 99, 262104. [90] M. Jeppsson, K. A. Dick, H. A. Nilsson, N. Skold, J. B. Wagner, P. Caroff, L. Wernersson, J. Cryst. Growth 2008, 310, 5119. [91] Z. X. Yang, S. P. Yip, D. P. Li, N. Han, G. F. Dong, X. G. Liang, L. Shu, T. F. Hung, X. L. Mo, J. C. Ho, ACS Nano 2015, 9, 9268. [92] L. Ma, W. Hu, Q. L. Zhang, P. Y. Ren, X. J. Zhuang, H. Zhou, J. Y. Xu, H. L. Li, Z. P. Shan, X. X. Wang, L. Liao, H. Q. Xu, A. L. Pan, Nano Lett. 2014, 14, 694. [93] T. Luo, B. Liang, Z. Liu, X. M. Xie, Z. Luo, G. Z. Shen, Sci. Bull. 2015, 60, 101. [94] H. F. Bao, C. M. Li, X. Q. Cui, Q. L. Song, H. B. Yang, J. Guo, Nanotechnology 2008, 19, 335302. [95] Y. P. Li, F. Wei, Y. Ma, H. Zhang, Z. Gao, L. Dai, G. G. Qin, CrystEngComm 2013, 15, 6611. [96] R. X. Li, J. H. Yang, N. J. Huo, C. Fan, F. Y. Lu, T. F. Yan, Z. M. Wei, J. B. Li, ChemPhyChem 2014, 15, 2510. [97] R. X. Li, Q. Yue, Z. M. Wei, J. Mater. Chem. C 2013, 1, 5866. [98] Q. Yang, L. Chen, C. Hu, S. X. Wang, J. C. Zhang, W. D. Wu, J. Alloys Compd. 2014, 612, 301. [99] Y. Xi, C. G. Hu, X. M. Zhang, Y. Zhang, Z. L. Wang, Solid State Commu. 2009, 149, 1894. [100] J. F. Chao, S. M. Xing, Y. C. Zhao, S. L. Gao, Q. H. Song, L. X. Guo, D. Wang, T. L. Zhang, Solid State Sci. 2016, 61, 51. [101] G. J. Xiao, Q. F. Dong, Y. N. Wang, Y. M. Sui, J. J. Ning, Z. Y. Liu, W. J. Tian, B. B. Liu, G. T. Zou, B. Zou, RSC Adv. 2012, 2, 234. [102] F. X. Liang, C. W. Ge, T. F. Zhang, W. J. Xie, D. Y. Zhang, Y. F. Zou, K. Zheng, L. B. Luo, Nanophotonics 2017, 6, 494. 1700081 (13 of 14)