氮化鎵的寬能隙（3.4 eV）、高臨界電場(3.4 MV/cm) 、高電子飽和速度(2×107 cm/s)以及高熱導係數（2.3 W/cm．K）的材料特性使得在功率元件的應用上相較於矽材料有相當大的優勢。在近幾年來，成長於矽基板上之氮化鋁鎵/氮化鎵高電子遷移率蕭特基二極體已被廣泛研究與討論。其中，降低導通電壓為蕭特基二極體的重要特性之一，因為對於功率元件的應用而言，寬能隙特性所造成過大的導通電壓將造成能源的浪費且嚴重降低電路與系統運轉的效率。
本論文將呈現模擬與量測的結果。在模擬部分，我們利用Silvaco這套製程模擬軟體，模擬陽極的導通電壓與電場分佈。此外，透過兩種不同的陽極接觸（蕭特基與歐姆接觸），我們模擬在不同的矽基板摻雜以及有無AlN層（位於氮化鎵與矽基板之間）的情況下，施加正負偏壓後的垂直電場分佈以及電子濃度分佈，討論崩潰可能發生的位置以及電場分佈的差異。
在量測部分，本論文將利用陽極掘入技術來降低導通電壓，形成Γ形狀的結構，其中的蕭特基延伸類似於field-plate結構，可分散掘入後陽極周圍的電場。量測結果顯示，陽極掘入結構能夠同時改善導通電壓從1.2 V降至0.7 Ｖ以及崩潰電壓從1600 V 提升至2200 V。元件導通電壓的降低乃是由於金屬與二維電子氣的直接接觸進而增加穿隧機率。此外，高崩潰電壓可歸因於蝕刻後平整的側壁表面與2 m的蕭特基延伸有效減緩最大電場強度。

The material characteristics of Gallium Nitride used in the power device applications are superior than silicon owing to the wide bandgap (~3.4 eV), high critical electric field (3.4 MV/cm), high electron saturation velocity (2*107 cm/s), and high thermal conductivity (2.3 W/cm．K). Recently, many publications related to the AlGaN/GaN-on-Silicon Schottky Barrier Diodes (SBDs) have been discussed. One of the most critical issues is lowering the turn-on voltage owing to the wide bandgap nature of the material, which can increase the conduction loss and seriously degrade the efficiency of circuits and systems.
This thesis presents the simulation and measurement results. In the simulation, the Silvaco TCAD software is used to simulate the turn-on voltage and e-field distribution for that with/without anode recess. Also, by considering two different contacts (Schottky and ohmic) with different silicon substrate doping and with/without AlN layer (between GaN and Silicon), the vertical distribution of e-field and carrier concentration is simulated to discuss the breakdown location and the e-field distribution. In the measurement, the anode recess technology is employed to reduce the turn-on voltage, which forms a Γ-shaped electrode and acts similar to a field plate to alleviate the high electric field. The SBDs with anode-recessed structure is presented to simultaneously improve the turn-on voltage from 1.1 V to 0.7 V and the breakdown voltage (VBK) from 1600 to 2200 V. The turn-on voltage reduction can be attributed to the increased tunneling probability by directly contacting the 2DEG with Schottky metal. Also, the high VBK can be attributed to the smooth contact interface and the 2-μm Schottky extension to alleviate the peak e-field intensity.

第1章 緒論 1
1.1 研究背景跟動機 1
1.2 論文架構 2
1.3 氮化鎵基本特性 2
1.3.1 寬能隙 3
1.3.2 電子飽和速度 4
1.3.3 崩潰電壓跟導通電阻 5
1.4 本章總結 7
第2章 掘入及量測方法 8
2.1 歐姆接觸掘入 8
2.2 蕭特基接觸掘入 10
2.3 量測方法 12
2.3.1 傳輸長度量測方法 12
2.3.2 緩衝層漏電測試結構 13
2.3.3 原子力顯微鏡 14
2.4 結果與討論 17
2.4.1 不同的歐姆掘入深度對歐姆接觸的影響 17
2.4.2 不同的製程參數對蝕刻深度的影響 18
第3章 氮化鎵/氮化鋁鎵崩潰機制 20
3.1 矽基板氮化鎵元件的崩潰機制 21
3.2 閘極-汲極崩潰機制 22
3.3 緩衝層崩潰機制 22
3.4 垂直方向漏電機制 23
3.5 量測結果跟討論 26
3.5.1 緩衝層漏電流的量測結果 26
3.5.2 垂直漏電流的量測結果 28
3.6 本章總結 29
第4章 氮化鎵/氮化鋁鎵蕭特基二極體 30
4.1 元件設計 30
4.2 元件製程步驟 32
4.2.1 高台絕緣 34
4.2.2 歐姆接觸 35
4.2.3 蕭特基接觸 36
4.2.4 鈍化層 36
4.3 結果與討論 36
4.3.1 I-V直流特性 36
4.3.2 能障高度與理想因子 46
4.3.3 高功率特性 47
4.4 量測結果的比較 52
4.5 本章總結 52
第5章 GAN元件結構模擬 53
5.1 陽極端（歐姆接觸）正偏壓的垂直崩潰機制模擬 59
5.2 陽極端（歐姆接觸）負偏壓的垂直崩潰機制模擬 64
5.3 陽極端（蕭特基接觸）垂直崩潰機制模擬 67
5.4 本章總結 73
第6章 結論 74
6.1 總結 74
6.2 未來工作 74
參考文獻 76

[1] E. B.-Treidel, O. Hilt, R. Zhytnytska, A. Wentzel, C. Meliani, J. Würfl and G.Tränkle, “Fast-switching GaN-based lateral power Schottky barrier diodes with low onset voltage and strong reverse blocking,” IEEE Electron Device Lett., vol. 33, no. 3, pp. 357359, Mar. 2012.
[2] M Zhu, B. Song, M. Qi, Z. Hu, K. Nomoto, X. Yan, Y. Cao, W. Johnson, E. Kohn, D. Jena and H. G. Xing, “1.9-kV AlGaN/GaN lateral schottky barrier diodes on Silicon,” IEEE Electron Device Lett., vol. 36, no. 4, pp. 375-377, Apr. 2015.
[3] J. G. Lee, B. R Park, C. H. Cho, K. S. Seo and H. Y. Cha “Low Turn-On Voltage AlGaN/GaN-on-Si Rectifier With Gated Ohmic Anode,” IEEE Electron Device Lett., vol. 34, no. 2, pp.214216, February. 2013.
[4] W. Chen, K.-Y. Wong, W. Huang, and K. J. Chen, “High-performance AlGaN/ GaN lateral field-effect rectifiers compatible with high electron mobility transistors,” Appl. Phys. Lett., vol. 92, no. 25, pp. 253501, Jun. 2008.
[5] O. Ambacher, “Growth and applications of group III-nitrides,” Journal of Physics D (Applied Physics), vol. 31, pp. 2653-2710, 1998.
[6] M. Willander, M. Friesel, Q. Wahab, B. Straumal, “Silicon carbide and diamond for high temperature devices applications,” Journal of materials science: materials in electronics, pp. 1-25, 2006.
[7] B. Gelmont, K. Kim, and M. Shur, “Monte Carlo Simulation of electron transport in Gallium Nitride,” J. Appl. Phys., vol. 74, no. 3, pp. 1818-1821, 1993.
[8] B. J. Baliga, “Trends in power semiconductor devices,” IEEE Transaction on Electron Devices, 43(10), pp. 1717-1731, 1996.
[9] J. L. Hudgins, G. S. Simin, E. Santi and M.A. Khan, “An assessment of wide bandgap semiconductors for power devices,” IEEE trans. on power electronics, 18(3), pp. 907-914, 2003.
[10] M. E. Lin, Z. F. Fan, Z. Ma, L. H. Allen, and H. Morkoq Lin, “ Reactive ion etching of GaN using BCl3,” Appl. Phys. Lett. 64 (7), 14 Feb. ,pp. 887-888, 1994.
[11] C. F. Lin, H. C. Cheng, G. C. Chi, C. J. Bu, and M. S. Feng, “Improved contact performance of GaN film using Si diffusion,” Appl. Phys. Lett., vol. 76, no. 14, pp. 1878-1880, 2000.
[12] D. Buttari, A. Chini, G. Meneghesso, E. Zanoni, B. Moran, S. Heikman, N. Q. Zhang, L. Shen, R. Coffie, S. P. DenBaars, and U. K. Mishra, “Systematic characterization of Cl2 reactive ion etching for improved Ohmics in AlGaN/GaN HEMTs,” IEEE Electron Device Letters, vol. 23, no. 2, pp. 623-623, Feb. 2002.
[13] V. Desmaris, J. Eriksson, N. Rorsman, and H. Zirath, “Low-Resistance Si/Ti/ Al/Ni/Au multilayer Ohmic contact to undoped AlGaN/GaN heterostructures,” Electrochemical and Solid- State Letters, vol. 7, no. 4, pp. G72-G74, 2004.
[14] M. Hiroki, K. Nishimura, N. Watanabe, Y. Oda and T. Kobayashi , “Al/Ti/Al Ohmic contact to AlGaN/GaN heterostructure,” IEICE Technical Report ED, Nov. 2008.
[15] L. Wang, D. H. Kim, and I. Adesida , “Direct contact mechanism of Ohmic metallization to AlGaN/GaN heterostructures via Ohmic area recess etching,” Appl. Phys. Lett., 95, pp.172107-1~172107-3, 2009.
[16] M. Singh, Y. Zhang, J. Singh and U. Mishra, “Examination of tunnel junctions in the AlGaN / GaN system:consequences of polarization charge,” Appl. Phys. Lett., vol. 77, no. 12, pp.1867-1869, 2009.
[17] M. Kanamura, T. Ohki, T. Kikkawa, K. Imanishi, T. Imada, A. Yamada, and N. Hara , “Enhancement-Mode GaN MIS-HEMTs with n-GaN /i-AlN/n-GaN triple cap layer and high-k gate dielectrics,” IEEE Electron Device Letters, vol. 31, no. 3, pp.189-191, Mar. 2010.
[18] Y. Dora, A. Chakraborty, S. Heikman, L. McCarthy, S. Keller, S. P. DenBaars, and U. K. Mishra, “Effect of Ohmic contacts on buffer leakage of GaN transistors,” IEEE Electron Device Lett., vol. 27, no. 7, pp. 529-531, 2006.
[19] Z.-Q. Fang, D. C. Look, X.-L. Wang, Jung Han, F. A. Khan and I. Adesida, “Plasma-etching-enhanced deep centers in n-GaN grown by metal organic chemical-vapor deposition,” Appl. Phys. Lett., vol. 82, no. 10, pp. 1562-1564, Mar. 2003.
[20] Introduction to Bruker’s ScanAsyst and PeakForce Tapping AFM Technology, Bruker Corporation, 2011.
[21] N. Jalili, M. Dadfarnia, D. M. Dawson “ A fresh insight into the microcantilever -sample interaction problem in non-contact Atomic Force Microscopy ,” Journal of Applied Phys, vol.126, pp.327 - 335, Jun.2004.
[22] H. Ishida, D. Shibata, M. Yanagihara, Y. Uemoto, H. Matsuo, T. Ueda, T. Tanaka and D. Ueda, “Unlimited high breakdown voltage by Natural Super Junction of polarized semiconductor”, IEEE Electron Device Letters, Vol. 29, No. 10, Octor. 2008.
[23] S. Arulkumaran, T. Egawa, S. Matsui, and H. Ishikawa, “Enhancement of breakdown voltage by AlN buffer layer thickness in AlGaN/GaN high-electron-mobility transistors on 4 in. diameter silicon,” Applied Physics Letters, vol. 86, pp. 123503, Mar. 2005.
[24] Y. Dora, A. Chakraborty, L. McCarthy, S. Keller, S. P. DenBaars, and U. K. Mishra, “High breakdown voltage achieved on AlGaN/GaN HEMTs with integrated slant field plate,” IEEE Electron Device Letters, vol. 27, no. 9, pp. 713–715, Sep. 2006.
[25] H. Xing, Y. Dora, A. Chini, S. Heikman, S. Keller, and U. K. Mishra, “High breakdown voltage achieved by multiple field plates,” IEEE Electron Device Letters, vol. 25, no. 4, pp. 161–163, Apr. 2004.
[26] D. Visalli, M. V. Hove, P. Srivastava, J. Derluyn, J. Das, M. Leys, S.Degroote, K. Cheng, M. Germain, and G. Borghs, “Experimental and simulation study of breakdown voltage enhancement of AlGaN/GaN heterostructures by Si substrate removal,” Applied Physics Letters, vol.97, pp.113501, Mar.2010.
[27] P. Srivastava, J. Das, D. Visalli, J. Derluyn, M. Van Hove, P. E. Malinowski, D. Marcon, K. Geens, K. Cheng, S. Degroote, M. Leys, M. Germain, S. Decoutere, R. P. Mertens, and G. Borghs, “Record breakdown voltage (2200 V) of GaN DHFETs with 2 μm buffer thickness by local Si removal,” IEEE Electron Device Lett., vol. 32, no. 1, pp. 30–32, Jan. 2011.
[28] P. Srivastava, H. Oprins, M. Van Hove, J. Das, P. E. Malinowski, B. Bakeroot, D. Marcon, D. Visalli, X. Kang, K. Geens, J. Viaene, K. Cheng, M. Leys, I. De Wolf, S. Decoutere, R. P. Mertens, and G. Borghs, “Si trench around drain (STAD) technology of GaN-DHFETs on Si substrate for boosting power performance,” in Proc. IEEE IEDM, pp. 19.6.1–19.6.4 , Dec. 2011
[29] I. B. Rowena, S. L. Selvaraj and T. Egawa, “Buffer thickness contribution to suppress vertical leakage current with high breakdown field (2.3 MV/cm) for GaN on Si,” IEEE Electron Device Letter, vol. 32, no. 11, pp.1534-1536, Nov. 2011.
[30] J. Würfl, O. Hilt, E. Bahat-Treidel, R. Zhytnytska, K. Klein, P. Kotara,F. Brunner, A. Knauer, O. Krüger, M. Weyers, G. Tränkle “Technological approaches towards high voltage, fast switching GaN power transistors,” ECS Transactions, vol. 52, no. 1, pp.979-989, Nov. 2013.
[31] C. Zhou, Q. Jiang, S. Huang, and K. J. Chen, “Vertical leakage/breakdown mechanisms in AlGaN/GaN-on-si devices, IEEE Electron Device Letters, vol. 33, no. 8, pp. 1132–1134, Aug. 2012.
[32] B. Lu, E. L. Piner, and T. Palacios, “Breakdown mechanism in AlGaN/GaN HEMTs on Si substrate,” Device Research Conference (DRC), pp. 193–194, Jun. 2010.
[33] B. Boudart, Y Guhel, J. C. Pesant, P. Dhamelincourt and M. A. Poisson, “Raman characterization of Mg+ ion-implanted GaN,” J. Phys., Condens. Matter, vol. 16, no. 2, pp. s49-s55, Jan. 2004.
[34] T. Oishi, N. Miura, M. Suita, T. Nanjo, Y. Abe, “Highly resistive GaN layers formed by ion implantation of Zn along the c-axis,” J. Appl. Phys., vol. 94, no. 3, pp. 1662-1666, Aug. 2003.
[35] J. Y. Shiu, J.-C. Huang, V. Desmaris, C.-T. Chang, C.-Y Lu, K. Kumakura, T. Makimoto, H. Zirath, N. Rorsman and E. Y. Chang, “Oxygen ion implantation isolation planar process for AlGaN/GaN HEMTs,” IEEE Electron Device Lett., vol. 28, no. 6, pp. 476-478, Jun. 2007.
[36] Z. Yang, K. Li, J. Alperin, and W. I. Wang, “Nitrogen vacancy as the donor: experimental evidence in the ammonia-assisted molecular beam epitaxy of GaN,” J. Electrochem. Soc., Vol. 144, No. 10, Oct. 1997.
[37] M. Tajima and T. Hashizume, “Impact of gate and passivation structures on current collapse of AlGaN/GaN high-electron-mobility transistors under off-state- bias stress,” J. Appl. Phys., vol. 50, pp.061001, Jun. 2011.
[38] T. Hashizume, J. Kotani, and H. Hasegawa, “Leakage mechanism in GaN and AlGaN Schottky interfaces,” Applied Physics Letters, vol. 84,no.24, Jun. 2004.
[39] Y. W. Lian, Y. S. Lin, J. M. Yang, C. H. Cheng, and Shawn S. H. Hsu, “AlGaN/GaN Schottky barrier diodes on Silicon substrates with selective si diffusion for low onset voltage and high reverse blocking,” IEEE Electron Device Lett., vol. 34, no. 8, pp. 981-983, Jun. 2007.