1. State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology & Shaanxi Joint Key Laboratory of Graphene, School of Microelectronics Xidian University Xi'an 710071 Shaanxi China
2. Guangzhou Wide Bandgap Semiconductor Innovation Center, Guangzhou institute of technology Xidian University Guangzhou 510555 Guangdong China
3. Qinghai Huanghe Hydropower Development CO., LTD. Xining 810008 Qinghai China