School of Microelectronics,Xidian University,Xi'an 710071,China;
Key Laboratory of Wide Band Gap Semiconductor Materials and Devices of Ministry of Education,Xi'an 710071,China;
School of Microelectronics,Xidian University,Xi'an 710071,China;
Key Laboratory of Wide Band Gap Semiconductor Materials and Devices of Ministry of Education,Xi'an 710071,China;