Novel optoelectronic devices based on single semiconductor nanowires (nanobelts)
© Ye et al.; licensee Springer. 2012
Received: 17 November 2011
Accepted: 3 March 2012
Published: 13 April 2012
Semiconductor nanowires (NWs) or nanobelts (NBs) have attracted more and more attention due to their potential application in novel optoelectronic devices. In this review, we present our recent work on novel NB photodetectors, where a three-terminal metal–semiconductor field-effect transistor (MESFET) device structure was exploited. In contrast to the common two-terminal NB (NW) photodetectors, the MESFET-based photodetector can make a balance among overall performance parameters, which is desired for practical device applications. We also present our recent work on graphene nanoribbon/semiconductor NW (SNW) heterojunction light-emitting diodes (LEDs). Herein, by taking advantage of both graphene and SNWs, we have fabricated, for the first time, the graphene-based nano-LEDs. This achievement opens a new avenue for developing graphene-based nano-electroluminescence devices. Moreover, the novel graphene/SNW hybrid devices can also find use in other applications, such as high-sensitivity sensor and transparent flexible devices in the future.
Semiconductor single-crystalline nanowires (NWs) or nanobelts (NBs) can be grown on lattice mismatched substrates and constructed into devices with the bottom-up method on basically any substrates . Hence, compared to the conventional ones, semiconductor NW- or NB-based devices have the advantage of versatility in both the material and the device structure. So far, various semiconductor NW- or NB-based nanodevices have been emerging continuously [2–4]. Developing novel high-performance nano-optoelectronic devices is not only important in diverse device applications, but also has significant meaning in exploring and realizing optoelectronic integration.
In this review, we present our research work on two types of novel optoelectronic devices based on semiconductor NWs (NBs). One is semiconductor NB metal–semiconductor field-effect transistor (MESFET)-based photodetectors . In contrast to the common two-terminal single semiconductor NB (NW) photodetectors, the three-terminal NB MESFET-based photodetector can make a balance among overall performance parameters, which is desired for practical device applications. The other is novel multicolor light-emitting diodes (LEDs) based on graphene nanoribbon (GNR)/semiconductor nanowire (SNW) heterojunctions . Herein, ZnO, CdS, and CdSe NWs were employed for demonstration. At forward biases, the GNR/SNW heterojunction LEDs emitted light from ultraviolet (380 nm) to red (705 nm), which were determined by the bandgaps of the involved SNWs. This work opens a new avenue for developing diverse graphene-based optoelectronic devices . These two works may help to promote nano-optoelectronic integration in the future.
Single CdS NB MESFET photodetector
Comparison of the key parameters for the CdS NB (NW) photodetectors with different structures
Rise; fall time
746; 794 μs
6.0 × 103
approximately 20; approximately 20 μs
7.3 × 104
-; 320 ms
137; 379 μs
approximately 2.0 × 102
approximately 2.7 × 106
Figure 2d shows the on/off photocurrent response of the CdS NB MESFET-based photodetector measured at VG = −3.8 V, which is the threshold voltage of the MESFET under light illumination. We can see that the average dark current and photocurrent are about 26 fA and 70 nA, respectively, resulting in a Ilight/Idark as high as approximately 2.7 × 106. To the best of our knowledge, this is so far among the highest reported values for single NB (NW) photodetectors [3, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]. In addition, the photoresponse processes (both rise and decay processes) are quite fast, which have exceeded the detection limit (0.3 s) of the measurement apparatus (Keithley 4200, Cleveland, OH, USA).
The Rλ, defined as the photocurrent generated per unit power of incident light on the effective illuminated area of a photoconductor, and the external quantum efficiency (EQE), defined as the number of electrons detected per incident photon, are two critical parameters for photodetectors. The Rλ and EQE can be calculated with equations and , respectively. Here, ΔΙ is the difference between the photocurrent and the dark current, Pλ is the light power density, S is the effective illuminated area, h is Planck's constant, c is the velocity of light, e is the electronic charge, and λ is the light wavelength. Using ΔΙ = 7.0 × 10−8 A (measured from Figure 2d), Pλ = 5.3 mW/cm2S = 500 nm × 13 μm (measured from the inset of Figure 1a), λ = 488 nm, the Rλ and EQE of the CdS NB MESFET photodetector can be estimated to be approximately 2.0 × 102 A/W and 5.2 × 102, respectively.
In order to further investigate the detailed photoresponse times of the single CdS NB MESFET photodetector, we employed a 200-MHz digital oscilloscope (Tektronix DPO2024, Beaverton, OR, USA) with a 10-MΩ impedance and an optical chopper working at a frequency of 1,000 Hz, as shown in Figure 2e. From the close-up of the measured result shown in Figure 2f, the rise timer, defined as the time needed for the photocurrent to increase from 10 % ipeak to 90 % ipeak, is 137 μs and the decay timed, defined analogously, is 379 μs.
We attribute the overall high performance of our CdS NB MESFET-based photodetectors to the unique advantage of the MESFET structure. Compared to two-terminal photodetectors, there are two main advantages of the MESFET-based photodetectors. First, it has a much lower dark current because the applied negative gate voltage (in our case, the threshold voltage under illumination) helps to deplete the channel carriers. Second, this gate depletion effect will also cause a fast current recovery when the light is turned off. Consequently, the decay tail, which is normally observed in a two-terminal photodetectors, is suppressed in the MESFET-based photodetectors.
Multicolor GNR/SNW heterojunction LEDs
By taking advantage of both graphene and SNWs, we have fabricated, for the first time, the graphene-based nano-LED . This achievement opens a new avenue for developing graphene-based nano-electroluminescence devices. Moreover, the novel graphene/SNW hybrid devices can also find use in other applications, such as high-sensitivity sensor and transparent flexible devices in the future.
Both the n-type NWs [20–22] and the graphene  used in this work were synthesized via the CVD method. Before device fabrication, the graphenes were transferred by the stamp method with the help of polymethyl methacrylate  to Si/300-nm SiO2 substrates for Raman and electrical property characterizations, to quartz substrates for transparency characterization, and transferred to carbon-coated grids for high-resolution transmission electron microscopy (HRTEM) characterization (Tecnai F30, FEI, Eindhoven, The Netherlands). Their electrical properties were measured by a Hall effect measurement system (Accent HL5500, York, England).
It is worth noting that the GNR/NW structure has clear advantage over the conventional Schottky structure. For comparison, we have fabricated various metal/SNW Schottky structures, where the NWs used are identical to those reported in this work. Unfortunately, no EL can be observed in these structures. We attribute this to the well-known luminescence quenching effect caused by the involved metal . Moreover, in our face-to-face contact LED, the active region, where the radiative recombination occurs, is larger and the series resistance is smaller, compared to the crossed NWs or NW/Si pad heterojunction structures [20, 30, 31]. These merits may benefit high-efficiency EL and even electrically driven laser in the future.
We review two types of novel nano-optoelectronic devices developed in our group recently. One is the photodetector, which converts light to electric signals. Our MESFET-based photodetectors have ultrahigh Ilight/Idark (approximately 2.7 × 106) and fast response (rise time, approximately 137 μs; decay time, approximately 379 μs) simultaneously. The other is LED, which converts electric power to light. At forward biases, our novel GNR/SNW heterojunction LEDs emitted light with wavelengths varying from ultraviolet (380 nm) to red (705 nm), which were determined by the bandgaps of the involved SNWs. These two types of nano-optoelectronic devices may find diverse applications in future nano-optoelectronic integration.
This work was supported by the National Natural Science Foundation of China (nos. 61125402, 51172004, 11074006, 10874011, 50732001), the National Basic Research Program of China (nos. 2012CB932703, 2007CB613402), and the Fundamental Research Funds for the Central Universities.
- Yang PD, Yan RX, Fardy M: Semiconductor nanowire: what’s next? Nano Lett 2010, 10: 1529. 10.1021/nl100665rView ArticleGoogle Scholar
- Duan XF, Huang Y, Agarwal R, Lieber CM: Single-nanowire electrically driven lasers. Nature 2003, 421: 241. 10.1038/nature01353View ArticleGoogle Scholar
- Shen GZ, Chen D: One-dimensional nanostructures for photodetectors. Recent Pat Nanotechnol 2010, 4: 20. 10.2174/187221010790712101View ArticleGoogle Scholar
- Zhai TY, Fang XS, Li L, Bando Y, Golberg D: One-dimensional CdS nanostructures: synthesis, properties, and applications. Nanoscale 2010, 2: 168. 10.1039/b9nr00415gView ArticleGoogle Scholar
- Ye Y, Dai L, Wen XN, Wu PC, Pen RM, Qin GG: High-performance single CdS nanobelt metal–semiconductor field-effect transistor-based photodetectors. ACS Appl Mater Interfaces 2010, 2: 2724. 10.1021/am100661xView ArticleGoogle Scholar
- Ye Y, Gan L, Dai L, Meng H, Wei F, Dai Y, Shi ZJ, Yu B, Guo XF, Qin GG: Multicolor graphene nanoribbon/semiconductor nanowire heterojunction light-emitting diodes. J Mater Chem 2011, 21: 11760. 10.1039/c1jm11441gView ArticleGoogle Scholar
- Bonaccorso F, Sun Z, Hasan T, Ferrari AC: Graphene photonics and optoelectronics. Nat Photon 2010, 4: 611. 10.1038/nphoton.2010.186View ArticleGoogle Scholar
- Kind H, Yan HQ, Messer B, Law M, Yang PD: Nanowire ultraviolet photodetectors and optical switches. Adv Mater 2002, 14: 158. 10.1002/1521-4095(20020116)14:2<158::AID-ADMA158>3.0.CO;2-WView ArticleGoogle Scholar
- Jie JS, Zhang WJ, Jiang Y, Meng XM, Li YQ, Lee ST: Photoconductive characteristics of single-crystal CdS nanoribbons. Nano Lett 1887, 2006: 6.Google Scholar
- Gao T, Li QH, Wang TH: CdS nanobelts as photoconductors. Appl Phys Lett 2005, 86: 173105. 10.1063/1.1915514View ArticleGoogle Scholar
- Zhai TY, Fang XS, Liao MY, Xu XJ, Li L, Liu BD, Koide Y, Ma Y, Yao JN, Bando Y, Golberg D: Fabrication of high-quality In2Se3 nanowire arrays toward high-performance visible-light photodetectors. ACS Nano 2010, 4: 1596. 10.1021/nn9012466View ArticleGoogle Scholar
- Fang XS, Xiong SL, Zhai TY, Bando Y, Liao MY, Gautam UK, Koide Y, Zhang XG, Qian YT, Golberg D: High-performance blue/ultraviolet-light-sensitive ZnSe-nanobelt photodetectors. Adv Mater 2009, 21: 5016. 10.1002/adma.200902126View ArticleGoogle Scholar
- Fang XS, Bando Y, Liao MY, Gautam UK, Zhi CY, Dierre B, Liu BD, Zhai TY, Sekiguchi T, Koide Y, Golberg D: Single-crystalline ZnS nanobelts as ultraviolet-light sensors. Adv Mater 2034, 2009: 21.Google Scholar
- Zhai TY, Liu HM, Li HQ, Fang XS, Liao MY, Li L, Zhou HS, Koide Y, Bando Y, Golberg D: Centimeter-long V2O5 nanowires: from synthesis to field-emission, electrochemical, electrical transport, and photoconductive properties. Adv Mater 2010, 22: 2547. 10.1002/adma.200903586View ArticleGoogle Scholar
- Li L, Wu PC, Fang XS, Zhai TY, Dai L, Liao MY, Koide Y, Wang HQ, Bando Y, Golberg D: Single-crystalline CdS nanobelts for excellent field-emitters and ultrahigh quantum-efficiency photodetectors. Adv Mater 2010, 22: 3161. 10.1002/adma.201000144View ArticleGoogle Scholar
- Zhou J, Gu YD, Hu YF, Mai WJ, Yeh PH, Bao G, Sood AK, Polla DL, Wang ZL: Gigantic enhancement in response and reset time of ZnO UV nanosensor by utilizing Schottky contact and surface functionalization. Appl Phys Lett 2009, 94: 191103. 10.1063/1.3133358View ArticleGoogle Scholar
- Wei TY, Huang CT, Hansen BJ, Lin YF, Chen LJ, Lu SY, Wang ZL: Large enhancement in photon detection sensitivity via Schottky-gated CdS nanowire nanosensors. Appl Phys Lett 2010, 96: 013508. 10.1063/1.3285178View ArticleGoogle Scholar
- Ye Y, Dai L, Wu PC, Liu C, Sun T, Ma RM, Qin GG: Schottky junction photovoltaic devices based on CdS single nanobelts. Nanotechonology 2009, 20: 375202. 10.1088/0957-4484/20/37/375202View ArticleGoogle Scholar
- Jin YZ, Wang JP, Sun BQ, Blakesley JC, Greenham NC: Solution-processed ultraviolet photodetectors based on colloidal ZnO nanoparticles. Nano Lett 2008, 8: 1649. 10.1021/nl0803702View ArticleGoogle Scholar
- Yang WQ, Huo HB, Dai L, Ma RM, Liu SF, Ran GZ, Shen B, Lin CL, Qin GG: Electrical transport and electroluminescence properties of n-ZnO single nanowires. Nanotechnology 2006, 17: 4868. 10.1088/0957-4484/17/19/015View ArticleGoogle Scholar
- Ye Y, Dai Y, Dai L, Shi ZJ, Liu N, Wang F, Fu L, Peng RM, Wen XN, Chen ZJ, Liu ZF, Qin GG: High-performance single CdS nanowire (nanobelt) Schottky junction solar cells with Au/graphene Schottky electrodes. ACS Appl Mater Interfaces 2010, 2: 3406. 10.1021/am1007672View ArticleGoogle Scholar
- Ye Y, Ma YG, Yue S, Dai L, Meng H, Li Z, Tong LM, Qin GG: Lasing of CdSe/SiO2 nanocables synthesized by the facile chemical vapor deposition method. Nanoscale 2011, 3: 3072. 10.1039/c1nr10392jView ArticleGoogle Scholar
- Gan L, Liu S, Li DN, Gu H, Cao Y, Shen Q, Wang ZX, Wang Q, Guo XF: Facile fabrication of the crossed nanotube-graphene junctions. Acta Phys – Chim Sin 2010, 26: 1151.Google Scholar
- Reina A, Jia XT, Ho J, Nezich D, Son H, Bulovic V, Dresselhaus MS, Kong J: Large area, few-layer graphene films on arbitrary substrates by chemical vapor deposition. Nano Lett 2010, 4: 2689.Google Scholar
- Castro Neto AH, Guinea F, Peres NMR, Novoselov KS, Geim AK: The electronic properties of graphene. Rev Mod Phys 2009, 81: 109. 10.1103/RevModPhys.81.109View ArticleGoogle Scholar
- Thomas D, Boettcher J, Burghard M, Kern K: Photocurrent distribution in graphene-CdS nanowire devices. Small 1868, 2010: 6.Google Scholar
- Liu C, Dai L, Ye Y, Sun T, Peng RM, Wen XN, Wu PC, Qin GG: High-efficiency color tunable n-CdSxSe1-x/p+-Si parallel-nanobelts heterojunction light-emitting diodes. J Mater Chem 2010, 20: 5011. 10.1039/c0jm00667jView ArticleGoogle Scholar
- Ma RM, Wei XL, Dai L, Liu SF, Chen T, Yue S, Li Z, Chen Q, Qin GG: Light coupling and modulation in coupled nanowire ring-Fabry-Pérot cavity. Nano Lett 2009, 9: 2679.Google Scholar
- Flynn RA, Kim CS, Vurgaftman I, Kim M, Meyer JR, Mäkinen AJ, Bussmann K, Cheng L, Choa FS, Long JP: A room-temperature semiconductor spaser operating near 1.5 μm. Opt Express 2011, 19: 8954. 10.1364/OE.19.008954View ArticleGoogle Scholar
- Zhong ZH, Qian F, Wang DL, Lieber CM: Synthesis of p-type gallium nitride nanowires for electronic and photonic nanodevices. Nano Lett 2003, 3: 343. 10.1021/nl034003wView ArticleGoogle Scholar
- Gudiksen MS, Lauhon LJ, Wang JF, Smith DC, Lieber CM: Growth of nanowire superlattice structures for nanoscale photonics and electronics. Nature 2002, 415: 617. 10.1038/415617aView ArticleGoogle Scholar
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