1. State Key Laboratory of Superlattices and Microstructure, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
2. State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
3. Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing, Guangxi, China
4. School of Electrical and Electronic Engineering, Tiangong University, 399 Binshuixi Road, Tianjin 300387, P. R. China