1. State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, No. A35, Qinghua East Road, Haidian District, Beijing 100083, China
2. Center of Materials Science and Optoelectronic Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
3. State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
4. School of Electrical and Electronic Engineering, TianGong University, No. 399 Binshui West Road, Xiqing District, Tianjin 300387, China