1. School of Opto-electronic Engineering, Zaozhuang University, Zaozhuang 277160, China
2. School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China
3. School of Semiconductor and Physics, North University of China, Taiyuan 030051, China
4. School of Physical Science and Engineering, Beijing Jiaotong University, Beijing 100044, China
5. School of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001, China