1. Engineering Research Center of Thin Film Optoelectronics Technology Ministry of Education Nankai University Tianjin 300350 China
2. Laboratory of Physical & Chemical Testing and Failure Analysis Ningbo Branch of Ordnance Science Institute of China Ningbo 315103 China
3. Suzhou Institute of Nano‐Tech and Nano‐Bionics (SINANO) Chinese Academy of Sciences Suzhou 215123 China
4. State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology School of Microelectronics Xidian University Xi'an 710071 China