1. State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University 1 , Xi’an 710071, China
2. Shaanxi Joint Key Laboratory of Graphene, School of Microelectronics, Xidian University 2 , Xi’an 710071, China
3. Science and Technology on Reliability Physics and Applications Technology of Electronic Component Laboratory 3 , Guangzhou 510000, China