1. State Key Laboratory of Wide Bandgap Semiconductor Devices and Integrated Technology, School of Microelectronics, Xidian University, Xi’an 710071, China
2. Xidian-Wuhu Research Institute, Wuhu 241002, China
3. Department of Electronic Engineering, Xi’an University of Technology, Xi’an 710048, China
4. School of Physics, Xidian University, Xi’an 710071, China