在本次實驗中，我們將活化技術與鈍化技術分別使用在氮化鎵材料之元件上。
我們使用快速熱退火(Rapid thermal annealing)與雷射退火的方式來活化p型摻雜之氮化鎵磊晶層，並且顯著地降低此層與金屬間的接觸電阻。霍爾量測中顯示，快速熱退火或是雷射退火的方式，普遍能幫助p型氮化鎵(鎂摻雜)的電洞濃度從1017/cm3上升至2 × 1017/cm3，另外，使用雷射退火搭配鎳金屬膜的磊晶片，能使接觸電阻由10-2 Ωcm2 降至1.6×10-4 Ωcm2，最後，我們將此組實驗的方式引用到元件上做驗證。在順向偏壓時，發現有使用與沒使用雷射退火技術的元件在導通電壓值(Turn on voltage)上比較，會出現接近7.5%的減少，此值是在電流密度為100 A/cm2的情況下所量得，因此，又再一次地驗證此方法是可行的。
另一方面，我們使用CHF3電漿來抑制p-i-n功率元件側壁上的漏電流，實驗結果顯示，在逆向偏壓時，崩潰電壓有接近20%的提升，另外，元件之微分電阻在比較片與電漿處理過後的片子上可以得到分別為0.5 mΩ-cm2和0.48 mΩ-cm2，最後，我們在CHF3電漿處理過後的元件上得到非常高的Baliga品質因子為827 MW/cm2，這可以說是目前成長在藍寶石上的氮化鎵材料之p-i-n功率元件裡，最好的一個實驗結果。

In this work appropriate activation and passivation techniques have been introduced to p-GaN and applied to improve the electric characteristics of GaN p-i-n diodes. In order to better activate the p-GaN to further reduce the contact resistance, the rapid thermal annealing (RTA) and laser annealing system are studied. It is shown that RTA or laser annealing of Mg-doped GaN (about 0.5 um in thickness) in general helps activate acceptors and increase the average hole concentration by a factor of about 2 from low to mid of 1017/cm3 determined by the Hall measurement. Use of laser annealing of p-GaN coated with Ni and removal afterwards prior to depositing conventional Ni/Au ohmic-contact films, however, greatly improves the contact resistance from 10-2 to 1.6×10-4 Ωcm2. As a result, the forward voltage of p-i-n diodes can be as low as 3.7 V with a current density at 100 A/cm2 which is a 7.5 % reduction compared with control sample. The trifluoromethane-containing plasma is used to passivate the mesa surfaces and suppress the surface current leakage of GaN p-i-n rectifiers. Reduction of surface leakage enhances the reverse blocking voltage by 20% (from 509 to 630 V) measured at J＝1 A/cm2. Differential forward resistances of control samples and plasma-treated ones are 0.5 mΩ-cm2 and 0.48 mΩ-cm2, respectively, and an excellent Baliga’s Figure-of-merit of 827 MW/cm2 is achieved for GaN diodes fabricated on sapphire substrates.

[1] T.-T. Kao, J. Kim, Y.-C. Lee, M.-H. Ji, T. Detchprohm, R. D. Dupuis, and S.-C. Shen, “Homojunction GaN p-i-n Rectifiers with Ultra-low On-state Resistance,” CS MANTECH Tech. Dig., 157 (2014).
[2] T.G. Zhu, D.J.H. Lambert, B.S. Shelton, M.M. Wong, U. Chowdhury, Ho Ki Kwon and R.D. Dupuis, “High-voltage GaN pin vertical rectifiers with 2um thick i-layer,” Electron. Lett., 36, 1971 (2000).
[3] X. A. Cao, H. Lu, S. F. LeBoeuf, C. Cowen, S. D. Arthur, and W. Wang, “Growth and characterization of GaN PiN rectifiers on free-standing GaN,” Appl. Phys. Lett., 87, 053503 (2005).
[4] J.G. Yang and K. Yang, “GaN-based pin diodes for microwave switching IC applications,” 48, 650 (2012).
[5] J.B. Limb, D. Yoo, J.-H. Ryou, W. Lee, S.-C. Shen, and R.D. Dupuis, “High performance GaN pin rectifiers grown on free-standing GaN substrates,” Electron. Lett., 42, 1313 (2006).
[6] Y. Hatakeyama, K. Nomoto, N. Kaneda, T. Kawano, T. Mishima, and T. Nakamura, “Over 3.0 GW/cm2 Figure-of-Merit GaN p-n Junction Diodes on Free-Standing GaN Substrates,” Electron Device Lett., 32, 1674 (2011).
[7] K. Mochizuki, K. Nomoto, Y. Hatakeyama, H. Katayose, T. Mishima, N. Kaneda, T. Tsuchiya, A. Terano, T. Ishigaki, T. Tsuchiya, R. Tsuchiya, and T. Nakamura, “Photon-recycling GaN p-n Diodes Demonstrating Temperature-independent, Extremely Low On-resistance,” IEDM Tech. Dig., 26.3.1 (2011).
[8] Y. Hatakeyama, K. Nomoto, A. Terano, N. Kaneda, T. Tsuchiya, T. Mishima, and T. Nakamura, “High-Breakdown-Voltage and Low-Specific-on-Resistance GaN p–n Junction Diodes on Free-Standing GaN Substrates Fabricated Through Low-Damage Field-Plate Process,” Jpn. J. Appl. Phys., 52, 028007 (2013).
[9] I. C. Kizilyalli, A. P. Edwards, H. Nie, D. Disney, and D. Bour, “High Voltage Vertical GaN p-n Diodes With Avalanche Capability,” Trans. Electron Devices, 60, 3067 (2013).
[10] I. C. Kizilyalli, A. P. Edwards, O. Aktas, T. Prunty, and D. Bour, “Vertical Power p-n Diodes Based on Bulk GaN,” Trans. Electron Devices, 62, 414 (2015).
[11] N. Kaminski, O. Hilt, “SiC and GaN Devices – Competition or Coexistence?” CIPS (2012).
[12] I. Waki, H. Fujioka, M. Oshima, H. Miki, and A. Fukizawa, “Low-temperature activation of Mg-doped GaN using Ni films,” Appl. Phys. Lett. 78, 2899 (2001).
[13] C. Y. Hu, J. P. Ao, M. Okada and Y. Ohno, “Annealing with Ni for ohmic contact formation on ICP-etched p-GaN,” Electronics Lett. 44, 2 (2008).
[14] T. Wei, J. Wang, N. Liu, H. Lu, Y. Zeng, G. Wang, and J. Li, “Catalytic Activation of Mg-Doped GaN by Hydrogen Desorption Using Different Metal Thin Layers,” Jpn. J. Appl. Phys. 49, 100201 (2010).
[15] C. Y. Hsu, W. H. Lan and Y. S. Wu, “Thermal Annealing Effect Between Ni Film and Mg-Doped GaN Layer,” Jpn. J. Appl. Phys. 45, 6256–6258 (2006).
[16] Y. J. Lin, W. F. Liu, and C. T. Lee, “Excimer-laser-induced activation of Mg-doped GaN layers,” Appl. Phys. Lett. 84, 2515 (2004).
[17] S. J. Rhee, S. Kim, C. W. Sterner, J. O. White, and S. G. Bishop, “Excimer laser annealing of Er-implanted GaN,” J. Appl. Phys. 90, 2760 (2001).
[18] M. S. Oh, D. K. Hwang, J. H. Lim, C. G. Kang, and S. J. Park, “Low resistance nonalloyed Ni/Au Ohmic contacts to p-GaN irradiated by KrF excimer laser,” Appl. Phys. Lett. 89, 042107 (2006).
[19] W. C. Lai, M. Yokoyama, S. J. Chang, J. D. Guo, C. H. Shen, T. Y. Chen, W. C. Tsai, J. S. Tsang, S. H. Chan and S. M. Sze, “Optical and Electrical Characteristics of CO2-Laser-Treated Mg-Doped GaN Film,” Jpn. J. Appl. Phys. 39, L1138–L1140 (2000).
[20] Dieter k. Schroder, “Semiconductor material and Device Characterization,” John Wiley & Sons, Inc. Third Edition, pp. 140-141 (2006).
[21] K. K. Thornber, “Applications of scaling to problems in high‐field electronic transport,” J. Appl. Phys. 52, 279 (1981).
[22] H. W. Jang, T. Sands, and J. L. Lee, “Effects of KrF excimer laser irradiation on metal contacts to n -type and p -type GaN,” J. Appl. Phys. 94, 3529 (2003).
[23] L. S. Yu, D. Qiao, L. Jia, S. S. Lau, Y. Qi, and K. M. Lau, “Study of Schottky barrier of Ni on p-GaN,” Appl. Phys. Lett. 79, 4536 (2001).
[24] T. Hino, S. Tomiya, T. Miyajima, K. Yanashima, S. Hashimoto, and M. Ikeda, “Characterization of threading dislocations in GaN epitaxial layers,” Appl. Phys. Lett. 76, 3421 (2000).
[25] H. Marchand, L. Zhao, N. Zhang, B. Moran, R. Coffie, U. K. Mishra, J. S. Speck, S. P. DenBaars, and J. A. Freitas, “Metalorganic chemical vapor deposition of GaN on Si(111): Stress control and application to field-effect transistors,” J. Appl. Phys. 89, 7846 (2001).
[26] V. A. Dmitriev, “GaN Based p-n Structures Grown on SiC Substrates,” MRS Internet J. Nitride Semicond. Res. 1, 29 (1996).
[27] Jae-Chul Song, Seon-Ho Lee, In-Hwan Lee, Kyeong-Won Seol, Santhakumar Kannappan, Cheul-Ro Lee, “Characteristics comparison between GaN epilayers grown on patterned and unpatterned sapphire substrate (0 0 0 1),” J. Crystal Growth 308, 321 (2007).
[28] Dong-SingWuu, Hsueh-WeiWu, Shih-TingChen, Tsung-YenTsai, XinheZheng, Ray-HuaHorng, “Defect reduction of laterally regrown GaN on GaN/patterned sapphire substrates,” J. Crystal Growth 311, 3063 (2009).
[29] Ismail H. Oğuzman, Enrico Bellotti, Kevin F. Brennan, Ján Kolnı́k, Rongping Wang, and P. Paul Ruden, “Theory of hole initiated impact ionization in bulk zincblende and wurtzite GaN ,” Appl. Phys. Lett. 87, 7827 (1997).
[30] Hyunsoo Kim, Jaehee Cho, Yongjo Park, and Tae-Yeon Seong, “Leakage current origins and passivation effect of GaN-based light emittingdiodes fabricated with Ag p-contacts,” Appl. Phys. Lett. 92, 092115 (2008).