[1] Ishikawa H, Kobayashi S, Koide Y, et al. Effects of surface treatments and metal work functions on electrical properties at p-GaN/metal interfaces ［J］. J. Appl. Phys., 1997, 81(3):1315-1322.

[2] Koide Y, Maeda T, Kawakami T, et al. Effects of annealing in an oxygen ambient on electrical properties of Ohmic contacts to p-type GaN ［J］. J. Electron. Mater., 1999, 28(3):341-346.

[3] Kim H, Kim D J, Park S J, et al. Effect of an oxidized Ni/Au p contact on the performance of GaN/InGaN multiple quantum well light-emitting diodes ［J］. J. Appl. Phys., 2001, 89(2):1506-1508.

[4] Lee S H, Son H K, Kim S J, et al. High brightness GaN-based LEDs using ITO/n+-InGaN/InGaN superlattice/n+-GaN/p-GaN tunneling junction ［J］. Phys. Stat. Sol.(A), 2004, 201(12):2726-2729.

[5] Horng R H, Wuu D S, Lien Y C, et al. Low-resistance and high-transparency Ni/ITO Ohmic contacts to p-type GaN ［J］. Appl. Phys. Lett., 2001, 79(18):2925-2927.

[6] Kim S Y, Jang H W, Lee J L. Effect of an indium-tin-oxide overlayer on transparent Ni/Au Ohmic contact on p-type GaN ［J］. Appl. Phys. Lett., 2003, 82(1):61-63.

[7] Pan S M, Tu R C, Fan Y M, et al. Enhanced output power of InGaN-GaN light-emitting diodes with high-transparency nickel-oxide-indium-tin-oxide ohmic contacts ［J］. IEEE Photon. Technol. Lett., 2003, 15(5):646-648.

[8] Igasaki Y, Kanma H. Argon gas pressure dependence of the properties of transparent conducting ZnO∶Al films deposited on glass substrates ［J］. Appl. Surf. Sci., 2001, 169(170):508-511.

[9] Nakahara K, Tamura K, Sakai M, et al. Improved external efficiency InGaN-based light-emitting diodes with transparent conductive Ga-doped ZnO as p-electrodes ［J］. Jpn. J. Appl. Phys., 2004, 43(2A):L180-L182.

[10] Wang W J, Li X F, Zhang J H. Effect of ITO interface modulation layer on the performances of LEDs with Ga-doped ZnO electrode ［J］. Chin. J. Lumin.(发光学报), 2012, 33(2):211-215 (in Chinese).

[11] Wang S F, Li X F, Zhang J H. Effects of surface and chemical treatment and annealing on p-GaN/ZnO∶Ga contact ［J］. Chin. J. Lumin.(发光学报), 2010, 31(6):848-853 (in Chinese).

[12] Song J O, Kyong K, Seong J P, et al. Highly low resistance and transpartent Ni/ZnO Ohmic contacts to p-type GaN ［J］. Appl. Phys. Lett., 2003, 83(3):479-481.

[13] Byung D A, Sang H O, Choong H L, et al. Influence of thermal annealing ambient on Ga-doped ZnO thin films ［J］. J. Crystal Growth, 2007, 309(2):128-133.

[14] Kim H K, Yi M S, Lee S N. Low-resistance and highly transparent Ag/IZO Ohmic contact to p-type GaN ［J］. Thin Solid Films, 2009, 517(14):4039-4042.

[15] Song J O, Kwak J S, Park Y, et al. Ohmic and degradation mechanisms of Ag contacts on p-type GaN ［J］. Appl. Phys. Lett., 2005, 86(6):062104-1-3.

[16] Tian M M, Fan Y, Liu X Y. Fabrication and characteristics of transparent conducting bismuth-doped thin indium oxide Film ［J］. Chin. J. Lumin.(发光学报), 2010, 31(4):605-608 (in Chinese).

[17] Raju N, Kumar K J, Subrahmanyam A. Physical properties of silver oxide thin films by pulsed laser deposition: Effect of oxygen pressure during growth ［J］. J. Phys. D: Appl. Phys., 2009, 42(13):135411-1-5.

[18] Yang G H, Li X Y. Effect of the electrode layout on the silicon LED properties ［J］. Chin. J. Lumin.(发光学报), 2011, 32(4):374-377 (in Chinese).