1. College of Physics and Mathematics and Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science; University of Science and Technology Beijing; Beijing 100083 China
2. State Key Laboratory for Superlattices and Microstructures; Institute of Semiconductors; Chinese Academy of Sciences; Beijing 100083 China
3. College of Materials Science and Opto-Electronic Technology; University of Chinese Academy of Sciences; Beijing 100049 China