1. Key Laboratory of Microelectronic Devices & Integrated TechnologyInstitute of Microelectronics of Chinese Academy of Sciences Beijing 100029 China
2. University of Chinese Academy of Sciences Beijing 100049 China
3. Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM) Nanjing 211800 China
4. Key Laboratory of Wide Band Gap Semiconductor TechnologySchool of Advanced Materials and NanotechnologyXidian University Xi'an 710071 China