1. Institute of Semiconductors, South China Normal University, Guangzhou 510631, P.R. China
2. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, P.R. China
3. College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, P.R. China
4. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, P.R. China
5. Department of physics, Henan Normal University, Xinxiang 453007, P.R. China
6. Guangdong Provincial Key Laboratory of Chip and Integration Technology, Guangzhou 510631, P.R. China