1. Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu, Sichuan 610200, China
2. Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang, Sichuan 621999, China
3. Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
4. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
5. Department of Physics Science and Technology, School of Science, Wuhan University of Technology, Wuhan 430070, China