1. Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Northwestern Polytechnical University, Xi’an 710072, China
2. State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi’an 710071, China
3. Qinghai Huanghe Hydropower Development Co., Ltd., Xining Solar Power Branch, Xining 810007, China