1. Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of Microelectronics Xidian University Xi'an 710071 China
2. State Key Laboratory of Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai 200083 China
3. Hangzhou Institute for Advanced Study University of Chinese Academy of Sciences No.1, Sub-Lane Xiangshan, Xihu District 310024 Hangzhou China