1. Ningbo Institute of Material Technology and Engineering Chinese Academy of Sciences Ningbo 315201 P. R. China
2. Key Laboratory of Semiconductor Materials Science Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 P. R. China
3. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
4. School of Materials Sun Yat‐sen University Guangzhou 510275 P. R. China