本論文內容主要探討氮化鋁鎵/氮化鎵場效電晶體使用不同的磊晶表面層對電性的影響進行分析。實驗研究部分分為兩個主題， (1)使用不同活化條件的p型氮化鎵磊晶表面層製作的蕭特基閘極場效電晶體，元件製作前先經過分別為700度5/10/15分鐘氮氣環境中進行活化條件，實驗目的為利用不同的活化條件來活化摻雜於氮化鎵磊晶表面層內的鎂離子，進而改善元件閘極漏電流與暫態特性。(2)使用三種磊晶表面層製作的氮化鋁鎵/氮化鎵金氧半場效電晶體，分別為氮化鎵磊晶表面層(GaN cap)、 p型氮化鎵磊晶表面層(p-GaN cap)、氮化矽磊晶表面層(in-situ SiN cap) ，實驗目的為利用不同的磊晶表面層來提升元件的崩潰電壓和改善元件的閘極漏電流與暫態特性，並尋求取代GaN cap的材料。
不同活化條件的p型氮化鎵磊晶表面層製作的蕭特基閘極場效電晶體，其中p-GaN cap在700℃15分鐘氮氣環境中進行活化條件所製作的元件上有低的閘極漏電流2.74×10-6 A、(I_on/I_off )電流比值為9.06×107、低的次臨界斜率76 mV/dec、較小的電流崩塌現象、和最大的元件崩潰電壓(在汲極電流1 mA/mm下約為1380 V)。其在動態特性方面，元件在汲極電壓100 V下動態電阻比值皆比p-GaN cap 700℃- 10 min與p-GaN cap 700℃- 5 min好。最後利用矽基板偏壓的方式去觀察元件在進行切換開關時電子被表面缺陷或緩衝層缺陷捕捉的情形，其中在p-GaN cap 700℃- 15 min活化條件下的元件在量測結果上觀察到有較不嚴重的表面缺陷暫態行為。
三種磊晶表面層製作的氮化鋁鎵/氮化鎵金氧半場效電晶體，具備in-situ SiN cap元件上有低的閘極漏電流4.16×10-8 A、(I_on/I_off )電流比值為3.83×109、低的次臨界斜率91 mV/dec、較小的電流崩塌現象、較低的介面缺陷密度(Dit)值、最大的元件崩潰電壓(在汲極電流1 mA/mm下約為1248 V)。在動態特性方面，in-situ SiN cap元件在汲極電壓100 V下動態電阻比值皆比p-GaN cap與GaN cap元件好。最後利用矽基板偏壓的方式去觀察元件在進行切換開關暫態分析時，電子被表面缺陷或緩衝層缺陷捕捉的影響程度，其中在in-situ SiN cap元件在量測結果上觀察到比其他二種磊晶表面層元件有較少的表面缺陷，但有較多的緩衝層缺陷，推論元件特性受到表面缺陷影響較大。雖然具p-GaN cap元件的特性比in-situ SiN cap元件較差，但是特性相近，而傳統GaN cap元件特性遠不如上述二種。

This study focused on AlGaN/GaN FETs with different cap layers. There were two main parts in this research: (1) HEMTs with p-GaN cap under different activation conditions before device fabrication including 5/10/15 minutes in N2 at 700℃. The purpose was to activate Mg ions in p-GaN cap layer to improve performance on gate leakage and dynamic characteristics. (2) AlGaN/GaN MIS-HEMTs with three kinds of caps including GaN cap, p-GaN cap and in-situ SiN cap. The purpose was to reduce gate leakage, enhance breakdown voltages and dynamic characteristics by alternative cap-layers.
HEMTs with p-GaN cap under different activation conditions showed device with 700C-15min activation has best performanve. Gate leakage of 2.74×10-6 mA/mm, (Ion /𝐼𝑜𝑓𝑓) current ratio of 9.06×107, 76 mV/dec of Subthreshold Swing, and breakdown voltage of 1380 V were observed. For transient characteristics, device with 700C-15min activation showed best performance among all activation conditions.
MIS-HEMT with in-situ SiN cap showed gate leakage of 4.16×10-8 mA/mm, (Ion /𝐼𝑜𝑓𝑓) current ratio of 3.83×107, Subthreshold Swing of 91 mV/dec and breakdown voltage of 1248 V. For transient characteristics, MIS-HEMT with in-situ SiN cap showed the best performance than devices with p-GaN and GaN caps when stress drain voltages being less than 100 V. By using substrate bias scheme, surface trapping behavior is more significant than buffer traps in transient characteristics in this study. Although MIS-HEMT with in-situ SiN cap showed the best performance in DC and transient characteristics, but MIS-HEMT with p-GaN cap showed similar characteristics. Oppoaitely, MIS-HEMT with GaN cap showed the worst device characteristics.

[1] U. K. Mishra, L. Shen, T. E. Kazior, and Y. Wu, “GaN Power Devices for Micro Inverters,”Proceedings of the IEEE, No. 2, February 2008.
[2] N. Kaminski, and O. Hilt, “SiC and GaN devices – wide bandgap is not all the same,” IET Circuits Devices Syst, Vol. 8, Iss. 3, pp. 227–236, May 2014.
[3] H. Huang, Y. C. Liang, G. S. Samudra, T. Chang, and C. Huang, “Effects of Gate Field Plates on the Surface State Related Current Collapse in AlGaN/GaN HEMTs,”IEEE Transactions on Power Electronics, vol. 29, no. 5, May 2014.
[4] P. Kordos, J. Bernat, and M. Marso, “Impact of layer structure on performance of unpassivated AlGaN/GaN HEMT,”Electronics Letters, Vol. 40, Iss. 1, pp. 438–441, March 2005.
[5] T. Zine-eddine, H. Zahra, and M. Zitouni, “DC and RF characteristics of AlGaN/GaN HEMT and MOS-HEMT,” International Conference on Electrical Engineering, December 2015.
[6] C. Liu, E. F. Chor, and L.S. Tan, “Enhanced device performance of AlGaN/GaN HEMTs using HfO2 high-kdielectric for surface passivation and gate oxide,” Semiconductor Science and Technology, Vol. 22, Number. 5, March 2007.
[7] T. Hashizume, S. Ootomo, and H. Hasegawa, “Suppression of current collapse in insulated gate AlGaN/GaN heterostructure field-effect transistors using ultrathin Al2O3 dielectric,” Applied Physics Letters, Vol. 83, Number. 14, October 2003.
[8] D. Deen, D. Storm, D. Meyer, D. S. Katzer, R. Bass, S Binari, and T Gougousi, “AlN/GaN HEMTs with high-κ ALD HfO2 or Ta2O5 gate insulation,” Physica. Status Solidi C, No. 7–8, 2420–2423, May 2011.
[9] A.Fontser, A.Perez-Tomas, P.Godignon, and J.Millan, “High Voltage Low Ron In-situ SiN/Al0.35GaN0.65/GaN-on-Si Power HEMTs Operation up to 300 oC,” Proceedings of the European Solid-State Device Research Conference, September 2012.
[10] S. Yoshida, Y. Sakaida, J. T. Asubar, H. Tokuda, and M. Kuzuhara, “Current Collapse in AlGaN/GaN HEMTs with a GaN Cap Layer,” Future of Electron Devices, Kansai (IMFEDK), 2015 IEEE International Meeting for, June 2015.
[11] T. Chang, T. Hsiao, C. Huang, W. Kuo, S. Lin, G. S. Samudra, and Y. C. Liang, “Phenomenon of Drain Current Instability on p-GaN Gate AlGaN/GaN HEMTs,” IEEE Transactions on Electron Devices, Vol 62, issue 2, September 2014.
[12] H. Huang, Y. C. Liang, G. S. Samudra, T. Chang, and C. Huang, “Effects of Gate Field Plates on the Surface State Related Current Collapse in AlGaN/GaN HEMTs,” IEEE Teansactions on Power Electronics, Vol. 29, No. 5, May 2014.
[13] M. T. Hasan, T. Asano, H. Tokuda, and M. Kuzuhara, “Current Collapse Suppression by Gate
Field-Plate in AlGaN/GaN HEMTs,” IEEE Electron Device Letters, Vol. 34, Issue. 11, September 2013.

[14] M. T. Hasan, T. Asano, H. Tokuda, and M. Kuzuhara, “Atomic Layer Epitaxy AlN for Enhanced AlGaN/GaN HEMT Passivation,” IEEE Electron Devvice Letters, Vol. 34, No. 9, September 2013.
[15] Z. Tang, S. Huang, Q. Jiang, S. Liu, C. Liu, and K. J. Chen, “High-Voltage (600-V) Low-Leakage Low-Current-Collapse AlGaN/GaN HEMTs With AlN/SiNx Passivation,” IEEE Electron Device Letters, Vol. 34, No. 3, March 2013.
[16] S. Arulkumaran, T. Egawa, H. Ishikawa, and T. Jimbo, “Surface passivation effects on AlGaN/GaN high-electron-mobility transistors with SiO2, Si3N4 , and silicon oxynitride,” Applied Physics Letters, Vol. 84, Number. 4, January 2004.
[17] Z. H. Liu, G. I. Ng, H. Zhou, S. Arulkumaran, and Y. K. T. Maung, “Reduced surface leakage current and trapping effects in AlGaN/GaN high electron mobility transistors on silicon with SiN/Al2O3 passivation,” Applied Physics Letters, Vol. 98, March 2011.
[18] G. Vanko, T. Lalinsky, S. Hascık, I. Ryger, Z. Mozolova, J. Skriniarova, M. Tomaska, I. Kostic, and A. Vincze, “Impact of SF6 plasma treatment on performance of AlGaN/GaN HEMT,” Elsevier, Vol. 84, Issue. 1, August 2009.
[19] M. F. Romero, A. Jimenez, F. G. Flores, S. Martín-Horcajo, F. Calle, and E.s Munoz, “Impact of N2 Plasma Power Discharge on AlGaN/GaN HEMT Performance,” IEEE Transactions on Electron Devices, Vol. 59, Issue. 2, December 2011.
[20] D. J. Meyer, J. R. Flemish, and J. M. Redwing, “Pre-passivation Plasma Surface Treatment Effects on Critical Device Electrical Parameters of AlGaN/GaN HEMTs,” Cs Mantech Conference, April 2008.
[21] D. S. Lee, J. W. Chung, H. Wang, X. Gao, S. Guo, P. Fay, and T. Palacios, “245-GHz InAlN/GaN HEMTs With Oxygen Plasma Treatment,” IEEE Electron Device Letters, Vol. 32, No. 6, June 2011.
[22] T. Katsuno, M. Kanechika, K. Itoh, K. Nishikawa, T. Uesugi, and T. Kachi, “Improvement of Current Collapse by Surface Treatment and Passivation Layer in p-GaN Gate GaN High-Electron-Mobility Transistors,” Japanese Journal of Applied Physics, Vol. 52, March 2013.
[23] X. Wang, S. Huang, Y.Zheng, K. Wei, X. Chen, G. Liu, T. Yuan,W. Luo, L. Pang, H. Jiang, J. Li, C. Zhao, H. Zhang, and X. Liu, “Robust SiNx/AlGaN Interface in GaN HEMTs Passivated by Thick LPCVD-Grown SiNx Layer,” IEEE Electron Device Letters, VOL. 36, NO. 7, July 2015.
[24] M. Kuroda, T. Murata, S. Nakazawa, T. Takizawa, M. Nishijima, M. Yanagihara, T. Ueda, and T. Tanaka, “High fmax with High Breakdown Voltage in AlGaN/GaN MIS-HFETs Using In-situ SiN as Gate Insulators,” IEEE Compound Semiconductor Integrated Circuits Symposium, October 2008.
[25] B. A. Hull, S. E. Mohney, H. S. Venugopalan, and J. C. Ramer, “Influence of oxygen on the activation of p-type GaN,” Applied Physics Letters, VOL. 76, Number. 16, April 2000.
[26] T. WEN, S. LEE, W. LEE1, T CHEN2, S CHAN2 and J. TSANG, “Activation of p-Type GaN in a Pure Oxygen Ambient,” Japanese Journal of Applied Physics, VOL. 40, pp. 495-497 16, February 2001.
[27] S. ARULKUMARAN, T. EGAWA, and H. ISHIKAWA, “Studies on the Influences of i-GaN, n-GaN, p-GaN and InGaN Cap Layers in AlGaN/GaN High-Electron-Mobility Transistors,” Japanese Journal of Applied Physics, VOL. 44, No. 5A, pp. 2953-2960, May 2005.
[28] T. R. Prunty, J. A. Smart, E. N. Chumbes, B. K. Ridley, L.F. Eastman, and J.R. Shealy, “Passivation of AIGaN/GaN Heterostructures with Silicon Nitride For Insulated Gate Transistors,” High Performance Devices, 2000. Proceedings. 2000 IEEE/Cornell Conference on, February 2000.
[29] J. Derluyn, S. Boeykens, K. Cheng, R. Vandersmissen, J. Das, W. Ruythooren,S. Degroote, M. R. Leys, M. Germain, and G. Borghs, “Improvement of AlGaN/ GaN high electron mobility transistor structures by in situ deposition of a Si3N4 surface layer,” Journal of Applied Physics, VOL. 98, September 2005.
[30] P. Moens, C. Liu, A. Banerjee, P. Vanmeerbeek, P. Coppens, H. Ziad, A. Constant, Z. Li, H. De Vleeschouwer, J. Roig-Guitart, P. Gassot, F. Bauwens, E. De Backer, B. Padmanabhan, A. Salih, J. Parsey, and M. Tack, “An Industrial Process for 650V rated GaN-on-Si Power Devices using in-situ SiN as a Gate Dielectric,” 2014 IEEE 26th International Symposium on Power Semiconductor Devices & IC's (ISPSD), June 2014.
[31] B.P. Downey, D.J. Meyer, D.S. Katzer, T.M. Marron, M. Pan, and X. Gao, “Effect of SiNx gate insulator thickness on electrical properties of SiNx/In0.17Al0.83N/AlN/GaN MIS–HEMTs,” Elsevier, January 2015.
[32] M. J. Anand, G. I. Ng, S. Vicknesh, S. Arulkumaran, and K. Ranjan, “Effect of SiNx gate insulator thickness on electrical properties of SiNx/In0.17Al0.83N/AlN/GaN MIS–HEMTs,” physica Status Solidi C, No. 11, pp. 1421-1425, October 2013.
[33] O. Ambacher, J. Smart, J. R. Shealy, N. G. Weimann, K. Chu, M. Murphy, W. J. Schaff, and L. F. Eastman, “Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN/GaN heterostructures,” Journal of Applied Physics, VOL. 85, Number6, March 1999.
[34] D. Balaz, “Current Collapse and Device Degradation in AlGaN/GaN Heterostructure Field Effect Transistors,” University of Glasgow, 2010.
[35] J. W. P. Hsu, M. J. Manfra, R. J. Molnar, B. Heying, and J. S. Speck, “Direct imaging of reverse-bias leakage through pure screw dislocations in GaN films grown by molecular beam epitaxy on GaN templates,” Applied Physics Letters, VOL. 81, Number. 1, July 2002.
[36] B. Heying, X. H. Wu, S. Keller, Y. Li, D. Kapolnek, B. P. Keller,S. P. DenBaars, and J. S. Speck, “Role of threading dislocation structure on the x-ray diffraction peak widths in epitaxial GaN films,” Applied Physics Letters, VOL. 68, Number. 1, January 1996.
[37] Z. Tang, S. Huang, X. Tang, B. Li, and K. J. Chen, “Influence of AlN Passivation on Dynamic ON-Resistance and Electric Field Distribution in High-Voltage AlGaN/GaN-on-Si HEMTs,” IEEE Transactions on Electron Devvice, Vol. 61, No. 8, August 2014.
[38] S.Agnihotri, S. Ghosh, A. Dasgupta, S. A. Ahsan, S K.handelwal, and Y. S. Chauhan, “Modeling of Trapping Effects in GaN HEMTs,” Advanced Materials and Processes for RF and THz Applications (IMWS-AMP), 2015 IEEE MTT-S International Microwave Workshop Series on, July 2015.
[39] Z. Tang, S. Huang, X. Tang, B. Li, and K. J. Chen, “Mechanisms responsible for dynamic ON-resistance in GaN high-voltage HEMTs,” 2012 24th International Symposium on Power Semiconductor Devices and ICs, June 2012.
[40] A. Armstrong, A. R. Arehart, D. Green, U. K. Mishra, J. S. Speck, and S. A. Ringel, “Impact of deep levels on the electrical conductivity and luminescence of gallium nitride codoped with carbon and silicon,” Journal of Applied Physics, VOL. 98, September 2005.
[41] M. Gassoumi, O. Fathallah , C. Gaquiere, and H. Maaref , “Analysis of deep levels in AlGaN/GaN/Al2O3 heterostructures by CDLTS under a gate pulse,” Elsevier, VOL. 405, Issue. 9, pp. 2337-2339 , May 2010.
[42] Y. Tokuda, “Traps in MOCVD n-GaN Studied by Deep Level Transient Spectroscopy and Minority Carrier Transient Spectroscopy,” Cs Mantech Conference, May 2014.
[43] M. Gassoumi, B. Grimbert, C. Gaquiere, and H. Maaref, “Evidence of surface states for AlGaN/GaN/SiC HEMTs passivated Si3N4 by CDLTS,” Semiconductors, VOL. 46, Issue. 3, pp. 382-385 , March 2012.
[44] D. Bisi, M. Meneghini, C. d. Santi, A. Chini, M. Dammann, P. Brückner, M. Mikulla, G. Meneghesso, and Enrico Zanoni , “Deep-Level Characterization in GaN HEMTs-Part I: Advantages and Limitations of Drain Current Transient Measurements,” IEEE Transactions on Electron Devices, VOL. 60, No. 10, pp. 2337-2339 , October 2013.
[45] Z.-Q. Fang, J. W. Hemsky, D. C. Look, and M. P. Mack , “Electron-Irradiation-Induced Deep Level in n-Type GaN,” Applied Physics Letters, VOL.72, No. 4, January 1998.
[46] M. GASSOUMI, B. GRIMBERT, M. A. POISSON, J. FONTAINE, M. A. ZAIDI, C. GAQUIERE, and H. MAAREF, “Deep level investigation by capacitance and conductance transient spectroscopy in AlGaN/GaN/SiC HEMTs,” Journal of Optoelectronics and Advanced Materials, VOL.11, No. 11, pp. 1713-1717 November 2009.
[47] M. Meneghini, P. Vanmeerbeek, R. Silvestri, S. Dalcanale, A. Banerjee, D. Bisi, E. Zanoni, G. Meneghesso, and P. Moens, “Temperature-Dependent Dynamic RON in GaN-Based MIS-HEMTs: Role of Surface Traps and Buffer Leakage,” IEEE Transactions on Electron Devices, VOL. 62, No. 3, March 2015.
[48] C. Mizue, Y. Hori, M. Miczek, and T. Hashizume, “Capacitance–Voltage Characteristics of Al2O3/AlGaN/GaN Structures and State Density Distribution at Al2O3/AlGaN Interface,” Japanese Journal of Applied Physics, VOL. 50, Number. 2R, February 2011.
[49] S. Huang, Q. Jiang, S. Yang, Z. Tang, and K. J. Chen, “Mechanism of PEALD-Grown AlN Passivation for AlGaN/GaN HEMTs: Compensation of Interface Traps by Polarization Charges,” IEEE Electrin Device Letters, VOL. 34, Number. 2, February 2013.
[50] Z. H. Liu, G. I. Ng, S. Arulkumaran, Y. K. T. Maung, K. L. Teo, “Improved two-dimensional electron gas transport characteristics in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor with atomic layer-deposited Al2O3 as gate insulator,” Appl. Phys. Lett., 2009.