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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 18 — Aug. 27, 2012
  • pp: 20748–20753
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Enhancement of ultraviolet detecting by coupling the photoconductive behavior of GaN nanowires and p-n junction

Nishuang Liu, Weiwei Tian, Xianghui Zhang, Jun Su, Qi Zhang, and Yihua Gao  »View Author Affiliations


Optics Express, Vol. 20, Issue 18, pp. 20748-20753 (2012)
http://dx.doi.org/10.1364/OE.20.020748


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Abstract

The giant improvement of ultraviolet response behavior of a conventional GaN p-n film structured detector by the incorporation of slanted GaN nanowires is reported. The GaN nanowires/p-n film structure shows great photoresponse performance, exhibiting a short response time <0.1 s and a high sensitivity, being stable and reproducible with an on/off current contrast ratio as high as 1800 at zero bias under 365 nm ultraviolet light irradiation. Via carefully analyzing the experiment result and the band diagram of the device, the enhancement can be predominantly attributed to the photogenerated electrons in the slanted GaN nanowires.

© 2012 OSA

Over the last decade, III–V semiconductors materials have attracted extensive attentions in optical and electrical devices due to their superior properties [1

1. S. Guha and N. A. Bojarczuk, “Ultraviolet and violet GaN light emitting diodes on silicon,” Appl. Phys. Lett. 72(4), 415–417 (1998). [CrossRef]

, 2

2. E. Monroy, E. Munoz, F. J. Sanchez, F. Calle, E. Calleja, B. Beaumont, P. Gibart, J. A. Munoz, and F. Cusso, “High-performance GaN p-n junction photodetectors for solar ultraviolet applications,” Semicond. Sci. Technol. 13(9), 1042–1046 (1998). [CrossRef]

]. With a wide direct band gap (3.4 eV), high exciton binding energy, chemical and mechanical stability and quick saturation speed of the electronics drift, it has been demonstrated that GaN has a lot of applications such as nanolasers [3

3. M. Cazzanelli, D. Cole, J. F. Donegan, J. G. Lunney, P. G. Middleton, K. P. O'Donnell, C. Vinegoni, and L. Pavesi, “Photoluminescence of localized excitons in pulsed-laser-deposited GaN,” Appl. Phys. Lett. 73(23), 3390–3392 (1998). [CrossRef]

], ðeld-effect transistors [4

4. H. T. Ng, J. Han, T. Yamada, P. Nguyen, Y. P. Chen, and M. Meyyappan, “Single crystal nanowire vertical surround-gate field-effect transistor,” Nano Lett. 4(7), 1247–1252 (2004). [CrossRef]

], light-emitting diodes [5

5. C. J. Sun, M. Z. Anwar, Q. Chen, J. W. Yang, M. A. Khan, M. S. Shur, A. D. Bykhovski, Z. Liliental-Weber, C. Kisielowski, M. Smith, J. Y. Lin, and H. X. Xiang, “Quantum shift of band-edge stimulated emission in InGaN-GaN multiple quantum well light-emitting diodes,” Appl. Phys. Lett. 70(22), 2978–2980 (1997). [CrossRef]

, 6

6. P. Waltereit, H. Sato, C. Poblenz, D. S. Green, J. S. Brown, M. McLaurin, T. Katona, S. P. DenBaars, J. S. Speck, J. H. Liang, M. Kato, H. Tamura, S. Omori, and C. Funaoka, “Blue GaN-based light-emitting diodes grown by molecular-beam epitaxy with external quantum efficiency greater than 1.5%,” Appl. Phys. Lett. 84(15), 2748–2750 (2004). [CrossRef]

], diodes [7

7. P. Deb, H. Kim, Y. X. Qin, R. Lahiji, M. Oliver, R. Reifenberger, and T. Sands, “GaN nanorod Schottky and p-n junction diodes,” Nano Lett. 6(12), 2893–2898 (2006). [CrossRef] [PubMed]

], electric generators [8

8. C. T. Huang, J. H. Song, W. F. Lee, Y. Ding, Z. Y. Gao, Y. Hao, L. J. Chen, and Z. L. Wang, “GaN nanowire arrays for high-output nanogenerators,” J. Am. Chem. Soc. 132(13), 4766–4771 (2010). [CrossRef] [PubMed]

, 9

9. L. Lin, C. H. Lai, Y. F. Hu, Y. Zhang, X. Wang, C. Xu, R. L. Snyder, L. J. Chen, and Z. L. Wang, “High output nanogenerator based on assembly of GaN nanowires,” Nanotechnology 22(47), 475401 (2011). [CrossRef] [PubMed]

], ðeld emitters [10

10. R. D. Underwood, S. Keller, U. K. Mishra, D. Kapolnek, B. P. Keller, and S. P. DenBaars, “GaN field emitter array diode with integrated anode,” J. Vac. Sci. Technol. B 16(2), 822–825 (1998). [CrossRef]

, 11

11. S. G. Hao, G. Zhou, J. Wu, W. H. Duan, and B. L. Gu, “Spin-polarized electron emitter: Mn-doped GaN nanotubes and their arrays,” Phys. Rev. B 69(11), 113403 (2004). [CrossRef]

], UV photosensors [12

12. J. L. Li, Y. Xu, T. Y. Hsiang, and W. R. Donaldson, “Picosecond response of gallium-nitride metal-semiconductor-metal photodetectors,” Appl. Phys. Lett. 84(12), 2091–2093 (2004). [CrossRef]

]. For photodetector applications, high on/off current ratio, fast response and recovery, and large photoresponse current are desirable sensor characteristics. Due to that the photoconductive gained from a single GaN nanowire (NW) was three orders of magnitude larger than that of GaN film [13

13. R. S. Chen, H. Y. Chen, C. Y. Lu, K. H. Chen, C. P. Chen, L. C. Chen, and Y. J. Yang, “Ultrahigh photocurrent gain in m-axial GaN nanowires,” Appl. Phys. Lett. 91(22), 223106 (2007). [CrossRef]

], photodetectors based on one dimensional (1D) GaN nanostructures have attracted much attention recently and have been studied by many research groups.

While in this paper, simply via growing slanted GaN NWs on GaN film which is composed of a thin p-GaN film (about 400 nm thick GaN:Mg film) and a thick n-GaN film (about 1.3 μm thick GaN:Si film), the superiority of GaN NWs' excellent photoconductive property and built-in electric field existing between thin p-GaN film and a thick n-GaN film have been coupled, and the UV photoresponse properties have been ultimately improved. Moreover, via carefully analyzing the experiment result and the band diagram of the device, the enhancement mechanism is accordingly analyzed and discussed.

The slanted GaN NWs were synthesized in a conventional furnace with a horizontal quartz tube, which composed of two heating area, zone I and zone II. Ga particles were placed into a ceramic crucible. Then the crucible was put in the center of zone II which has the highest temperature, and a 5 nm-thick-Au coated GaN/sapphire film was placed at the site of 6 cm from the crucible. The synthesis processes were performed in two steps: first, the furnace was washed with Ar gas (high flow) three times and then flowed with Ar gas (100 sccm) over ~1 hour under 100 Pa through zone I to zone II. Second, a mixture of NH3 (20 sccm) and Ar (20 sccm) was substituted for the original Ar gas flow while the temperature of zone I was gradually increased to 1100 °C and the temperature of zone II to 900 °C over 35 min and then kept constant during 30 min. The quartz tube chamber was kept at a pressure of 2000 Pa during this process. Then, the whole quartz tube was taken out from the furnace and cooled to room temperature. Light yellow product was observed on the surface of the substrate.

Field emission scanning electronic microscope (FESEM) and transmission electron microscope (TEM) equipped with x-ray energy dispersion analysis system (EDS) was used for microstructural characterizations. To characterize the ultraviolet photoresponse properties, Ag (50 nm thick) electrodes were deposited by e-beam evaporator through a shadow mask on the GaN NWs as well as Ni (50 nm thick) on the n-GaN film. Meanwhile, in order to guarantee the quality of electrode contact, an insulating PMMA layer was spun on the sample as a block layer before depositing the metal contact. This process was similar to the Au (50 nm thick) electrodes deposited on ZnO NW reported by R. Ghosh and D. Basak [20

20. R. Ghosh and D. Basak, “Electrical and ultraviolet photoresponse properties of quasialigned ZnO nanowires/p-Si heterojunction,” Appl. Phys. Lett. 90(24), 243106 (2007). [CrossRef]

].

X-ray diffraction (XRD) spectrum of the product is shown in Fig. 1(a)
Fig. 1 (a) X-ray diffraction spectrum of the product. Two crystal phases, namely, Al2O3 and hexagonal GaN, are indexed. (b) Top-view FESEM micrograph of the slanted GaN NWs. The inset shows the magnified view of the NWs.
. The XRD peaks observed in the spectrum can be indexed to (002), (102), (103), (112) and (004) of hexagonal wurzite GaN (JCPDS: 01-070-2544) with the lattice constants a = 0.3146 nm and c = 0.5125nm, the other peaks are relevant to the sapphire. The strong (002), (004) peaks partly come from the GaN film. SEM morphology in Fig. 1(b) shows that high-yield and uniformly grown GaN NWs more or less inclined to the substrate surface, so called “slanted”. The morphology is more orderly than the GaN nanowires synthesized by L.L. Low [21

21. L. L. Low, F. K. Yam, K. P. Beh, and Z. Hassan, “The influence of Ga source and substrate position on the growth of low dimensional GaN wires by chemical vapour deposition,” Appl. Surf. Sci. 257(23), 10052–10055 (2011). [CrossRef]

] probably due to the different substrate. The diameter of the nanowires is in the range of 80-170 nm and the length is about 4 μm.

The EDS spectrum from the individual nanowire is shown in Fig. 2(a)
Fig. 2 (a) EDS analysis of the individual NW. (b) TEM image of the GaN NWs. The inset shows the magnified view of the top.
. The N and Ga signals come from the NW and Au originates from the catalyst. It reveals GaN nanowire was successfully synthesized. Figure 2(b) shows the TEM image of an individual nanowire. We can find that the diameter of the bottom is large than the top, and catalyst particle is found on its tip. The straight nanowire has a length of approximate 4 μm.

The above-mentioned GaN nanowires were fabricated based on vapor-liquid-solid mechanism. It’s known that NH3 can be decomposed into NH, NH2, N and H2 above 900 °C. The Au film on the GaN film coagulated into nanodroplets which acted as energetic favorable sites for the adsorption of Ga vapor and decomposed species of NH3 to form Au-Ga-N alloy. GaN will precipitate and grow when the concentration of the Ga-N flux exceeded the saturation point in the Au-Ga-N alloy [22

22. T. Y. Kim, S. H. Lee, Y. H. Mo, H. W. Shim, K. S. Nahm, E. K. Suh, J. W. Yang, K. Y. Lim, and G. S. Park, “Growth of GaN nanowires on Si substrate using Ni catalyst in vertical chemical vapor deposition reactor,” J. Cryst. Growth 257(1-2), 97–103 (2003). [CrossRef]

, 23

23. X. Y. Han, Y. H. Gao, and X. H. Zhang, “One-dimensional GaN nanomaterials transformed from one-dimensional Ga2O3 and Ga nanomaterials,” Nano-Micro Lett. 1, 4–8 (2009).

].

The enhanced responsibility is probably attributed to the extra absorption of ultraviolet light by slanted GaN NWs and/or to the photo-generated carriers in the nanowires. It was reported by Chen et al. that a photoconductive gained from a single GaN NW was three orders of magnitude larger than that of GaN film [13

13. R. S. Chen, H. Y. Chen, C. Y. Lu, K. H. Chen, C. P. Chen, L. C. Chen, and Y. J. Yang, “Ultrahigh photocurrent gain in m-axial GaN nanowires,” Appl. Phys. Lett. 91(22), 223106 (2007). [CrossRef]

]. The schematic band diagrams as shown in Fig. 4
Fig. 4 The schematic band diagrams of the mechanism accounting for the enhancement achieved in the (a) With GaN NWs photodetector as compared to the (b)Without GaN NWs photodetector.
can elucidate the mechanism responsible for such enhancement. In equilibrium, the band alignment results in the formation of potential barriers across the NWs-p film and p-n junction where the barrier height is determined by the doping level of the respective terminals. When ultraviolet light illuminates, electron-hole pairs are generated in the NWs and the p-n depletion region. In the depletion region, the photogenerated electron-hole pairs are separated by the field, so that electrons drift to the n-GaN and holes to the p-GaN. This results in the accumulation of holes in the p-GaN which lowered the potential barrier of NWs-p film junction. So plenty of photogenerated electrons in NWs were injected through the thin p-GaN film into n-GaN film while the diffusion length [26

26. K. Jarašiūnas, T. Malinauskas, S. Nargelas, V. Gudelis, J. V. Vaitkus, V. Soukhoveev, and A. Usikov, “Layer thickness dependent carrier recombination rate in HVPE GaN,” Phys. Status Solidi B 247(7), 1703–1706 (2010). [CrossRef]

, 27

27. A. Dmitriev and A. Oruzheinikov, “The rate of radiative recombination in the nitride semiconductors and alloys,” J. Appl. Phys. 86(6), 3241–3246 (1999). [CrossRef]

] of the injected electrons is much longer than the p-GaN width. This contributes to an amplification of the initial photocurrent and responsibility enhancement over the p-n GaN film without GaN NWs. The mechanism is partly similar to the n/p/i/n photodetector reported by Kah-Wee Ang et al [28

28. K. W. Ang, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Low-voltage and high-responsivity germanium bipolar phototransistor for optical detections in the near-infrared regime,” IEEE Electron Device Lett. 29(10), 1124–1127 (2008). [CrossRef]

]. In our NWs/film photodetector, photogenerated electrons coming from NWs act as the major carriers. In addition, large scale of GaN nanowires on the GaN film may largely enhance the absorbing of light and accordingly the UV detecting efficiency due to the reason similar to ZnO electrodes for efficient light trapping in solar cells [29

29. C. Battaglia, J. Escarre, K. Soderstrom, M. Charriere, M. Despeisse, F. J. Haug, and C. Ballif, “Nanomoulding of transparent zinc oxide electrodes for efficient light trapping in solar cells,” Nat. Photonics 5(9), 535–538 (2011). [CrossRef]

].

In summary, slanted GaN NWs was synthesized on GaN p-n film/sapphire by a simple method, and then, the superiority of GaN NWs' excellent photoconductive property and built-in electric field existing between thin p-GaN film and a thick n-GaN film have been coupled, and the UV photoresponse properties have been ultimately improved. This work may provide a simple route to obtain high performance UV photodetectors.

Acknowledgment

This work was supported by the 973 Program (2011CB933300), NNSF (11074082), ‘111’ project (B07038) of China.

References and links

1.

S. Guha and N. A. Bojarczuk, “Ultraviolet and violet GaN light emitting diodes on silicon,” Appl. Phys. Lett. 72(4), 415–417 (1998). [CrossRef]

2.

E. Monroy, E. Munoz, F. J. Sanchez, F. Calle, E. Calleja, B. Beaumont, P. Gibart, J. A. Munoz, and F. Cusso, “High-performance GaN p-n junction photodetectors for solar ultraviolet applications,” Semicond. Sci. Technol. 13(9), 1042–1046 (1998). [CrossRef]

3.

M. Cazzanelli, D. Cole, J. F. Donegan, J. G. Lunney, P. G. Middleton, K. P. O'Donnell, C. Vinegoni, and L. Pavesi, “Photoluminescence of localized excitons in pulsed-laser-deposited GaN,” Appl. Phys. Lett. 73(23), 3390–3392 (1998). [CrossRef]

4.

H. T. Ng, J. Han, T. Yamada, P. Nguyen, Y. P. Chen, and M. Meyyappan, “Single crystal nanowire vertical surround-gate field-effect transistor,” Nano Lett. 4(7), 1247–1252 (2004). [CrossRef]

5.

C. J. Sun, M. Z. Anwar, Q. Chen, J. W. Yang, M. A. Khan, M. S. Shur, A. D. Bykhovski, Z. Liliental-Weber, C. Kisielowski, M. Smith, J. Y. Lin, and H. X. Xiang, “Quantum shift of band-edge stimulated emission in InGaN-GaN multiple quantum well light-emitting diodes,” Appl. Phys. Lett. 70(22), 2978–2980 (1997). [CrossRef]

6.

P. Waltereit, H. Sato, C. Poblenz, D. S. Green, J. S. Brown, M. McLaurin, T. Katona, S. P. DenBaars, J. S. Speck, J. H. Liang, M. Kato, H. Tamura, S. Omori, and C. Funaoka, “Blue GaN-based light-emitting diodes grown by molecular-beam epitaxy with external quantum efficiency greater than 1.5%,” Appl. Phys. Lett. 84(15), 2748–2750 (2004). [CrossRef]

7.

P. Deb, H. Kim, Y. X. Qin, R. Lahiji, M. Oliver, R. Reifenberger, and T. Sands, “GaN nanorod Schottky and p-n junction diodes,” Nano Lett. 6(12), 2893–2898 (2006). [CrossRef] [PubMed]

8.

C. T. Huang, J. H. Song, W. F. Lee, Y. Ding, Z. Y. Gao, Y. Hao, L. J. Chen, and Z. L. Wang, “GaN nanowire arrays for high-output nanogenerators,” J. Am. Chem. Soc. 132(13), 4766–4771 (2010). [CrossRef] [PubMed]

9.

L. Lin, C. H. Lai, Y. F. Hu, Y. Zhang, X. Wang, C. Xu, R. L. Snyder, L. J. Chen, and Z. L. Wang, “High output nanogenerator based on assembly of GaN nanowires,” Nanotechnology 22(47), 475401 (2011). [CrossRef] [PubMed]

10.

R. D. Underwood, S. Keller, U. K. Mishra, D. Kapolnek, B. P. Keller, and S. P. DenBaars, “GaN field emitter array diode with integrated anode,” J. Vac. Sci. Technol. B 16(2), 822–825 (1998). [CrossRef]

11.

S. G. Hao, G. Zhou, J. Wu, W. H. Duan, and B. L. Gu, “Spin-polarized electron emitter: Mn-doped GaN nanotubes and their arrays,” Phys. Rev. B 69(11), 113403 (2004). [CrossRef]

12.

J. L. Li, Y. Xu, T. Y. Hsiang, and W. R. Donaldson, “Picosecond response of gallium-nitride metal-semiconductor-metal photodetectors,” Appl. Phys. Lett. 84(12), 2091–2093 (2004). [CrossRef]

13.

R. S. Chen, H. Y. Chen, C. Y. Lu, K. H. Chen, C. P. Chen, L. C. Chen, and Y. J. Yang, “Ultrahigh photocurrent gain in m-axial GaN nanowires,” Appl. Phys. Lett. 91(22), 223106 (2007). [CrossRef]

14.

F. González-Posada, R. Songmuang, M. Den Hertog, and E. Monroy, “Room-temperature photodetection dynamics of single GaN nanowires,” Nano Lett. 12(1), 172–176 (2012). [CrossRef] [PubMed]

15.

G. S. Aluri, A. Motayed, A. V. Davydov, V. P. Oleshko, K. A. Bertness, N. A. Sanford, and M. V. Rao, “Highly selective GaN-nanowire/TiO(2)-nanocluster hybrid sensors for detection of benzene and related environment pollutants,” Nanotechnology 22(29), 295503 (2011). [CrossRef] [PubMed]

16.

X. H. Zhang, X. Y. Han, J. Su, Q. Zhang, and Y. H. Gao, “Well vertically aligned ZnO nanowire arrays with an ultra-fast recovery time for UV photodetector,” Appl. Phys., A Mater. Sci. Process. 107(2), 255–260 (2012). [CrossRef]

17.

H. Kang, J. Park, T. Choi, H. Jung, K. H. Lee, S. Im, and H. Kim, “n-ZnO:N/p-Si nanowire photodiode prepared by atomic layer deposition,” Appl. Phys. Lett. 100(4), 041117 (2012). [CrossRef]

18.

W. Y. Weng, T. J. Hsueh, S. J. Chang, S. B. Wang, H. T. Hsueh, and G. J. Huang, “A high-responsivity GaN nanowire UV photodetector,” IEEE J. Sel. Top. Quantum Electron. 17(4), 996–1001 (2011). [CrossRef]

19.

R. S. Chen, T. H. Yang, H. Y. Chen, L. C. Chen, K. H. Chen, Y. J. Yang, C. H. Su, and C. R. Lin, “High-gain photoconductivity in semiconducting InN nanowires,” Appl. Phys. Lett. 95(16), 162112 (2009). [CrossRef]

20.

R. Ghosh and D. Basak, “Electrical and ultraviolet photoresponse properties of quasialigned ZnO nanowires/p-Si heterojunction,” Appl. Phys. Lett. 90(24), 243106 (2007). [CrossRef]

21.

L. L. Low, F. K. Yam, K. P. Beh, and Z. Hassan, “The influence of Ga source and substrate position on the growth of low dimensional GaN wires by chemical vapour deposition,” Appl. Surf. Sci. 257(23), 10052–10055 (2011). [CrossRef]

22.

T. Y. Kim, S. H. Lee, Y. H. Mo, H. W. Shim, K. S. Nahm, E. K. Suh, J. W. Yang, K. Y. Lim, and G. S. Park, “Growth of GaN nanowires on Si substrate using Ni catalyst in vertical chemical vapor deposition reactor,” J. Cryst. Growth 257(1-2), 97–103 (2003). [CrossRef]

23.

X. Y. Han, Y. H. Gao, and X. H. Zhang, “One-dimensional GaN nanomaterials transformed from one-dimensional Ga2O3 and Ga nanomaterials,” Nano-Micro Lett. 1, 4–8 (2009).

24.

J. C. Carrano, T. Li, D. L. Brown, P. A. Grudowski, C. J. Eiting, R. D. Dupuis, and J. C. Campbell, “High-speed pin ultraviolet photodetectors fabricated on GaN,” Electron. Lett. 34(18), 1779–1781 (1998). [CrossRef]

25.

E. Monroy, F. Omnes, and F. Calle, “Wide-bandgap semiconductor ultraviolet photodetectors,” Semicond. Sci. Technol. 18(4), R33–R51 (2003). [CrossRef]

26.

K. Jarašiūnas, T. Malinauskas, S. Nargelas, V. Gudelis, J. V. Vaitkus, V. Soukhoveev, and A. Usikov, “Layer thickness dependent carrier recombination rate in HVPE GaN,” Phys. Status Solidi B 247(7), 1703–1706 (2010). [CrossRef]

27.

A. Dmitriev and A. Oruzheinikov, “The rate of radiative recombination in the nitride semiconductors and alloys,” J. Appl. Phys. 86(6), 3241–3246 (1999). [CrossRef]

28.

K. W. Ang, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Low-voltage and high-responsivity germanium bipolar phototransistor for optical detections in the near-infrared regime,” IEEE Electron Device Lett. 29(10), 1124–1127 (2008). [CrossRef]

29.

C. Battaglia, J. Escarre, K. Soderstrom, M. Charriere, M. Despeisse, F. J. Haug, and C. Ballif, “Nanomoulding of transparent zinc oxide electrodes for efficient light trapping in solar cells,” Nat. Photonics 5(9), 535–538 (2011). [CrossRef]

OCIS Codes
(040.5160) Detectors : Photodetectors
(250.0040) Optoelectronics : Detectors

ToC Category:
Detectors

History
Original Manuscript: June 7, 2012
Revised Manuscript: August 5, 2012
Manuscript Accepted: August 15, 2012
Published: August 24, 2012

Citation
Nishuang Liu, Weiwei Tian, Xianghui Zhang, Jun Su, Qi Zhang, and Yihua Gao, "Enhancement of ultraviolet detecting by coupling the photoconductive behavior of GaN nanowires and p-n junction," Opt. Express 20, 20748-20753 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-18-20748


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References

  1. S. Guha and N. A. Bojarczuk, “Ultraviolet and violet GaN light emitting diodes on silicon,” Appl. Phys. Lett.72(4), 415–417 (1998). [CrossRef]
  2. E. Monroy, E. Munoz, F. J. Sanchez, F. Calle, E. Calleja, B. Beaumont, P. Gibart, J. A. Munoz, and F. Cusso, “High-performance GaN p-n junction photodetectors for solar ultraviolet applications,” Semicond. Sci. Technol.13(9), 1042–1046 (1998). [CrossRef]
  3. M. Cazzanelli, D. Cole, J. F. Donegan, J. G. Lunney, P. G. Middleton, K. P. O'Donnell, C. Vinegoni, and L. Pavesi, “Photoluminescence of localized excitons in pulsed-laser-deposited GaN,” Appl. Phys. Lett.73(23), 3390–3392 (1998). [CrossRef]
  4. H. T. Ng, J. Han, T. Yamada, P. Nguyen, Y. P. Chen, and M. Meyyappan, “Single crystal nanowire vertical surround-gate field-effect transistor,” Nano Lett.4(7), 1247–1252 (2004). [CrossRef]
  5. C. J. Sun, M. Z. Anwar, Q. Chen, J. W. Yang, M. A. Khan, M. S. Shur, A. D. Bykhovski, Z. Liliental-Weber, C. Kisielowski, M. Smith, J. Y. Lin, and H. X. Xiang, “Quantum shift of band-edge stimulated emission in InGaN-GaN multiple quantum well light-emitting diodes,” Appl. Phys. Lett.70(22), 2978–2980 (1997). [CrossRef]
  6. P. Waltereit, H. Sato, C. Poblenz, D. S. Green, J. S. Brown, M. McLaurin, T. Katona, S. P. DenBaars, J. S. Speck, J. H. Liang, M. Kato, H. Tamura, S. Omori, and C. Funaoka, “Blue GaN-based light-emitting diodes grown by molecular-beam epitaxy with external quantum efficiency greater than 1.5%,” Appl. Phys. Lett.84(15), 2748–2750 (2004). [CrossRef]
  7. P. Deb, H. Kim, Y. X. Qin, R. Lahiji, M. Oliver, R. Reifenberger, and T. Sands, “GaN nanorod Schottky and p-n junction diodes,” Nano Lett.6(12), 2893–2898 (2006). [CrossRef] [PubMed]
  8. C. T. Huang, J. H. Song, W. F. Lee, Y. Ding, Z. Y. Gao, Y. Hao, L. J. Chen, and Z. L. Wang, “GaN nanowire arrays for high-output nanogenerators,” J. Am. Chem. Soc.132(13), 4766–4771 (2010). [CrossRef] [PubMed]
  9. L. Lin, C. H. Lai, Y. F. Hu, Y. Zhang, X. Wang, C. Xu, R. L. Snyder, L. J. Chen, and Z. L. Wang, “High output nanogenerator based on assembly of GaN nanowires,” Nanotechnology22(47), 475401 (2011). [CrossRef] [PubMed]
  10. R. D. Underwood, S. Keller, U. K. Mishra, D. Kapolnek, B. P. Keller, and S. P. DenBaars, “GaN field emitter array diode with integrated anode,” J. Vac. Sci. Technol. B16(2), 822–825 (1998). [CrossRef]
  11. S. G. Hao, G. Zhou, J. Wu, W. H. Duan, and B. L. Gu, “Spin-polarized electron emitter: Mn-doped GaN nanotubes and their arrays,” Phys. Rev. B69(11), 113403 (2004). [CrossRef]
  12. J. L. Li, Y. Xu, T. Y. Hsiang, and W. R. Donaldson, “Picosecond response of gallium-nitride metal-semiconductor-metal photodetectors,” Appl. Phys. Lett.84(12), 2091–2093 (2004). [CrossRef]
  13. R. S. Chen, H. Y. Chen, C. Y. Lu, K. H. Chen, C. P. Chen, L. C. Chen, and Y. J. Yang, “Ultrahigh photocurrent gain in m-axial GaN nanowires,” Appl. Phys. Lett.91(22), 223106 (2007). [CrossRef]
  14. F. González-Posada, R. Songmuang, M. Den Hertog, and E. Monroy, “Room-temperature photodetection dynamics of single GaN nanowires,” Nano Lett.12(1), 172–176 (2012). [CrossRef] [PubMed]
  15. G. S. Aluri, A. Motayed, A. V. Davydov, V. P. Oleshko, K. A. Bertness, N. A. Sanford, and M. V. Rao, “Highly selective GaN-nanowire/TiO(2)-nanocluster hybrid sensors for detection of benzene and related environment pollutants,” Nanotechnology22(29), 295503 (2011). [CrossRef] [PubMed]
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