1. Hunan Key Laboratory of Nanophotonics and Devices, School of Physics and Electronics, Central South University 1 , Changsha 410083, Hunan, China
2. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences 2 , Beijing 100083, China
3. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences 3 , Beijing 100049, China
4. School of Material and Energy, Guangdong University of Technology 4 , Guangzhou 510006, China
5. College of Semiconductors (College of Integrated Circuits), Hunan University 5 , Changsha 410082, Hunan, China