1. Key Lab of Semiconductor Materials Science Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 P. R. China
2. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
3. Shanghai Synchrotron Radiation Facility Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201204 P. R. China
4. Joint Lab of Digital Optical Chip Wuyi University Jiangmen 529020 P. R. China