1. Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
2. School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China
3. College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
4. Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Beijing 100083, China