1. Wide Bandgap Semiconductor Technology Disciplines State Key Laboratory, School of Advanced Materials and Nanotechnology, Xidian University, Xi'an 710071, China
2. School of Microelectronics, Xidian University, Xi'an 710071, China
3. Key Laboratory of Microelectronic Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China