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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 13 — Jun. 20, 2011
  • pp: 12658–12663
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High-performance GaN metal–insulator–semiconductor ultraviolet photodetectors using gallium oxide as gate layer

Ming-Lun Lee, T. S. Mue, F.W. Huang, J. H. Yang, and J. K. Sheu  »View Author Affiliations


Optics Express, Vol. 19, Issue 13, pp. 12658-12663 (2011)
http://dx.doi.org/10.1364/OE.19.012658


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Abstract

In this study, gallium nitride (GaN)-based metal–insulator–semiconductor (MIS) ultraviolet (UV) photodetectors (PDs) with a gallium oxide (GaOx) gate layer formed by alternating current bias-assisted photoelectrochemical oxidation of n-GaN are presented. By introducing the GaOx gate layer to the GaN MIS UV PDs, the leakage current is reduced and a much larger UV-to-visible rejection ratio (RUV/vis) of spectral responsivity is achieved. In addition, a bias-dependent spectral response results in marked increase of the RUV/vis with bias voltage up to ~105. The bias-dependent responsivity suggests the possible existence of internal gain in of the GaN MIS PDs.

© 2011 OSA

1. Introduction

2. Experiments

The GaN wafers used in this study were grown on c-face (0001) sapphire (Al2O3) substrates in a vertical low-pressure organometallic vapor phase epitaxy (OMVPE) reactor (Emcore D180). The layered structure of the GaN epitaxial wafers comprised a 30 nm thick GaN nucleation layer grown at 550 °C, a 2.3 μm thick Si-doped n+-GaN (n = 6 × 1018cm−3) layer, and a 1 μm thick lightly doped n-GaN (n = 3 × 1017cm−3) grown at 1050 °C. An Hg lamp with a power intensity of 350 mW/cm2 was used as the UV light source in the PEC oxidation experiments. Before oxidation, deionized H2O was first sprayed onto the surface of the mold. The front side of n-GaN sample was then adhered to the front side of the mold by gradually increasing the imprint pressure to 9 kg/cm2 in order to fill the mold pattern entirely with H2O. For the AC bias-assisted process, each bias cycle comprised a positive voltage pulse followed by a negative voltage pulse at a frequency of 2 Hz and a duty cycle of 90%. The growth rate of the PEC GaOx layers was 13.5 nm/min when the AC bias was 5 V. The GaOx layers were selectively grown on the n-GaN samples as the insulator layers for fabricating GaN MIS PDs. A semitransparent Ni/Au (5/10 nm) contact layer was deposited on the GaOx layer to serve as the gate metal, while Cr/Au (50/200 nm) contact metal was subsequently deposited onto the exposed n+-GaN layer and gate metal to serve as the Ohmic contact and electrode pad, respectively [9

9. J. K. Sheu, Y. K. Su, G. C. Chi, M. J. Jou, C. M. Chang, C. C. Liu, and W. C. Hung, “Inductively Coupled Plasma Etching of GaN using Cl2/Ar and Cl2/N2 Gases,” J. Appl. Phys. 85(3), 1970–1974 (1999). [CrossRef]

,10

10. M. L. Lee, J. K. Sheu, and C. C. Hu, “Nonalloyed Cr/Au-based Ohmic contacts to n-GaN,” Appl. Phys. Lett. 91(18), 182106 (2007). [CrossRef]

]. In this study, GaN MIS diodes with 70 nm and 130 nm thick GaOx gate layers were labeled PD-1 and PD-2, respectively. Figure 1(a) and (b)
Fig. 1 (a)schematic device structure (b)representative photograph of the fabricated circular photodetectors (c) schematic band diagram for depicting the mechanism of defect-assisted tunneling around the metal/GaOx/n-GaN interfaces.
show the schematic structure of the fabricated devices and a representative photograph of the fabricated devices, respectively. Devices without the GaOx gate layer were also prepared (labeled PD-3) for comparison. The room temperature current-voltage (I-V) characteristics of the fabricated PDs were measured by an HP4156 semiconductor parameter analyzer. Spectral responsivity of these GaN MIS PDs was measured using a Xe arc lamp and a calibrated monochromator as the light source.

3. Results and discussions

4. Conclusions

GaN-based MIS UV photodetectors with a GaOx gate layer formed by alternating current bias-assisted photoelectrochemical oxidation of n-GaN in H2O have been demonstrated in the current paper. The insertion of GaOx gate layer between the gate metal (Ni/Au) and n-GaN has been proven to significantly reduce leakage current and lead to a significant enhancement of UV-to-visible rejection ratio (RUV/vis). In addition, a marked bias-dependent spectral response in visible region could be effectively suppressed using the insertion layer; thus, the degradation of RUV/vis at high reverse bias becomes insignificant.

Acknowledgments

Financial support from the Bureau of Energy, Ministry of Economic Affairs of Taiwan, ROC. through grant No. 99-D0204-6 is appreciated. The authors would also like to acknowledge the National Science Council for the financial support of the research Grant Nos. NSC 97-2221-E-006-242-MY3, 98-2221-E-218-005-MY3 and 100-3113-E-006-015.

References and links

1.

E. Muñoz, E. Monroy, J. L. Pau, F. Calle, F. Omnès, and P. Gibart, “III nitrides and UV detection,” J. Phys. Condens. Matter 13(32), 7115–7137 (2001) (and references therein). [CrossRef]

2.

K. H. Chang, J. K. Sheu, M. L. Lee, S. J. Tu, C. C. Yang, H. S. Kuo, J. H. Yang, and W. C. Lai, “Inverted Al0.25Ga0.75N/GaN ultraviolet p-i-n photodiodes formed on p-GaN template layer grown by metalorganic vapor phase epitaxy,” Appl. Phys. Lett. 97(1), 013502 (2010) (and references therein). [CrossRef]

3.

G. Parish, S. Keller, P. Kozodoy, J. A. Ibbetson, H. Marchand, P. T. Fini, S. B. Fleischer, S. P. DenBaars, U. K. Mishra, and E. J. Tarsa, “High-performance (Al,Ga)N-based solar-blind ultraviolet p–i–n detectors on laterally epitaxially overgrown GaN,” Appl. Phys. Lett. 75(2), 247–249 (1999). [CrossRef]

4.

E. Monroy, M. Hamilton, D. Walker, P. Kung, F. J. Sánchez, and M. Razeghi, “High-quality visible-blind AlGaN p-i-n photodiodes,” Appl. Phys. Lett. 74(8), 1171–1173 (1999). [CrossRef]

5.

M. L. Lee, J. K. Sheu, W. C. Lai, S. J. Chang, Y. K. Su, M. G. Chen, C. J. Kao, J. M. Tsai, and G. C. Chi, “GaN Schottky barrier photodetectors with a low-temperature GaN cap layer,” Appl. Phys. Lett. 82(17), 2913–2915 (2003). [CrossRef]

6.

J. K. Sheu, M. L. Lee, and W. C. Lai, “Effect of low-temperature-grown GaN cap layer on reduced leakage current of GaN Schottky diodes,” Appl. Phys. Lett. 86(5), 052103 (2005). [CrossRef]

7.

M. L. Lee, T. S. Mue, J. K. Sheu, K. H. Chang, S. J. Tu, and T. H. Hsueh, “Effect of thermal annealing on GaN metal-oxide-semiconductor capacitors with gallium oxide gate layer,” J. Electrochem. Soc. 157(11), H1019–H1022 (2010) (and references therein). [CrossRef]

8.

C. T. Lee, H. W. Chen, and H. Y. Lee, “Metal–oxide–semiconductor devices using Ga2O3 dielectrics on n-type GaN,” Appl. Phys. Lett. 82(24), 4304–4306 (2003). [CrossRef]

9.

J. K. Sheu, Y. K. Su, G. C. Chi, M. J. Jou, C. M. Chang, C. C. Liu, and W. C. Hung, “Inductively Coupled Plasma Etching of GaN using Cl2/Ar and Cl2/N2 Gases,” J. Appl. Phys. 85(3), 1970–1974 (1999). [CrossRef]

10.

M. L. Lee, J. K. Sheu, and C. C. Hu, “Nonalloyed Cr/Au-based Ohmic contacts to n-GaN,” Appl. Phys. Lett. 91(18), 182106 (2007). [CrossRef]

11.

E. Monroy, F. Calle, J. L. Pau, E. Muñoz, F. Omnès, B. Beaumont, and P. Gibart, “AlGaN-based UV photodetectors,” J. Cryst. Growth 230(3–4), 537–543 (2001). [CrossRef]

12.

J. D. Hwang, G. H. Yang, Y. Y. Yang, and P. C. Yao, “Nitride-Based UV Metal–Insulator–Semiconductor Photodetector with Liquid-Phase-Deposition Oxide,” Jpn. J. Appl. Phys. 44(11), 7913–7915 (2005). [CrossRef]

13.

Y. Z. Chiou, Y. K. Su, S. J. Chang, J. Gong, C. S. Chang, and S. H. Liu, “The properties of photo chemical-vapor deposition SiO2 and its application in GaN metal-insulator semiconductor ultraviolet photodetectors,” J. Electron. Mater. 32(5), 395–399 (2003). [CrossRef]

14.

L. Binet and D. Gourier, “Origin of The Blue Luminescence of β-Ga2O3,” J. Phys. Chem. Solids 59(8), 1241–1249 (1998). [CrossRef]

15.

B. C. Hsu, S. T. Chang, T. C. Chen, P. S. Kuo, P. S. Chen, Z. Pei, and C. W. Liu, “A High Efficient 820 nm MOS Ge Quantum Dot Photodetector,” IEEE Electron Device Lett. 24(5), 318–320 (2003) (and references therein). [CrossRef]

16.

M. L. Lee, J. K. Sheu, and Y. R. Shu, “Ultraviolet bandpass Al0.17Ga0.83N/GaN heterojunction phototransitors with high optical gain and high rejection ratio,” Appl. Phys. Lett. 92(5), 053506 (2008). [CrossRef]

17.

P. C. Chang, C. L. Yu, S. J. Chang, Y. C. Lin, C. H. Liu, and S. L. Wu, “Low-Noise and High-Detectivity GaN-Based UV Photodiode With a Semi-Insulating Mg-Doped GaN Cap Layer,” IEEE Sens. J. 7(9), 1270–1273 (2007). [CrossRef]

OCIS Codes
(230.0040) Optical devices : Detectors
(230.0250) Optical devices : Optoelectronics
(230.5160) Optical devices : Photodetectors

ToC Category:
Detectors

History
Original Manuscript: April 14, 2011
Revised Manuscript: May 23, 2011
Manuscript Accepted: May 24, 2011
Published: June 15, 2011

Citation
Ming-Lun Lee, T. S. Mue, F.W. Huang, J. H. Yang, and J. K. Sheu, "High-performance GaN metal–insulator–semiconductor ultraviolet photodetectors using gallium oxide as gate layer," Opt. Express 19, 12658-12663 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-13-12658


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References

  1. E. Muñoz, E. Monroy, J. L. Pau, F. Calle, F. Omnès, and P. Gibart, “III nitrides and UV detection,” J. Phys. Condens. Matter 13(32), 7115–7137 (2001) (and references therein). [CrossRef]
  2. K. H. Chang, J. K. Sheu, M. L. Lee, S. J. Tu, C. C. Yang, H. S. Kuo, J. H. Yang, and W. C. Lai, “Inverted Al0.25Ga0.75N/GaN ultraviolet p-i-n photodiodes formed on p-GaN template layer grown by metalorganic vapor phase epitaxy,” Appl. Phys. Lett. 97(1), 013502 (2010) (and references therein). [CrossRef]
  3. G. Parish, S. Keller, P. Kozodoy, J. A. Ibbetson, H. Marchand, P. T. Fini, S. B. Fleischer, S. P. DenBaars, U. K. Mishra, and E. J. Tarsa, “High-performance (Al,Ga)N-based solar-blind ultraviolet p–i–n detectors on laterally epitaxially overgrown GaN,” Appl. Phys. Lett. 75(2), 247–249 (1999). [CrossRef]
  4. E. Monroy, M. Hamilton, D. Walker, P. Kung, F. J. Sánchez, and M. Razeghi, “High-quality visible-blind AlGaN p-i-n photodiodes,” Appl. Phys. Lett. 74(8), 1171–1173 (1999). [CrossRef]
  5. M. L. Lee, J. K. Sheu, W. C. Lai, S. J. Chang, Y. K. Su, M. G. Chen, C. J. Kao, J. M. Tsai, and G. C. Chi, “GaN Schottky barrier photodetectors with a low-temperature GaN cap layer,” Appl. Phys. Lett. 82(17), 2913–2915 (2003). [CrossRef]
  6. J. K. Sheu, M. L. Lee, and W. C. Lai, “Effect of low-temperature-grown GaN cap layer on reduced leakage current of GaN Schottky diodes,” Appl. Phys. Lett. 86(5), 052103 (2005). [CrossRef]
  7. M. L. Lee, T. S. Mue, J. K. Sheu, K. H. Chang, S. J. Tu, and T. H. Hsueh, “Effect of thermal annealing on GaN metal-oxide-semiconductor capacitors with gallium oxide gate layer,” J. Electrochem. Soc. 157(11), H1019–H1022 (2010) (and references therein). [CrossRef]
  8. C. T. Lee, H. W. Chen, and H. Y. Lee, “Metal–oxide–semiconductor devices using Ga2O3 dielectrics on n-type GaN,” Appl. Phys. Lett. 82(24), 4304–4306 (2003). [CrossRef]
  9. J. K. Sheu, Y. K. Su, G. C. Chi, M. J. Jou, C. M. Chang, C. C. Liu, and W. C. Hung, “Inductively Coupled Plasma Etching of GaN using Cl2/Ar and Cl2/N2 Gases,” J. Appl. Phys. 85(3), 1970–1974 (1999). [CrossRef]
  10. M. L. Lee, J. K. Sheu, and C. C. Hu, “Nonalloyed Cr/Au-based Ohmic contacts to n-GaN,” Appl. Phys. Lett. 91(18), 182106 (2007). [CrossRef]
  11. E. Monroy, F. Calle, J. L. Pau, E. Muñoz, F. Omnès, B. Beaumont, and P. Gibart, “AlGaN-based UV photodetectors,” J. Cryst. Growth 230(3–4), 537–543 (2001). [CrossRef]
  12. J. D. Hwang, G. H. Yang, Y. Y. Yang, and P. C. Yao, “Nitride-Based UV Metal–Insulator–Semiconductor Photodetector with Liquid-Phase-Deposition Oxide,” Jpn. J. Appl. Phys. 44(11), 7913–7915 (2005). [CrossRef]
  13. Y. Z. Chiou, Y. K. Su, S. J. Chang, J. Gong, C. S. Chang, and S. H. Liu, “The properties of photo chemical-vapor deposition SiO2 and its application in GaN metal-insulator semiconductor ultraviolet photodetectors,” J. Electron. Mater. 32(5), 395–399 (2003). [CrossRef]
  14. L. Binet and D. Gourier, “Origin of The Blue Luminescence of β-Ga2O3,” J. Phys. Chem. Solids 59(8), 1241–1249 (1998). [CrossRef]
  15. B. C. Hsu, S. T. Chang, T. C. Chen, P. S. Kuo, P. S. Chen, Z. Pei, and C. W. Liu, “A High Efficient 820 nm MOS Ge Quantum Dot Photodetector,” IEEE Electron Device Lett. 24(5), 318–320 (2003) (and references therein). [CrossRef]
  16. M. L. Lee, J. K. Sheu, and Y. R. Shu, “Ultraviolet bandpass Al0.17Ga0.83N/GaN heterojunction phototransitors with high optical gain and high rejection ratio,” Appl. Phys. Lett. 92(5), 053506 (2008). [CrossRef]
  17. P. C. Chang, C. L. Yu, S. J. Chang, Y. C. Lin, C. H. Liu, and S. L. Wu, “Low-Noise and High-Detectivity GaN-Based UV Photodiode With a Semi-Insulating Mg-Doped GaN Cap Layer,” IEEE Sens. J. 7(9), 1270–1273 (2007). [CrossRef]

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