1. State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors; Chinese Academy of Sciences; Beijing 100083 China
2. Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information; Huazhong University of Science and Technology (HUST); Wuhan 430074 China
3. Shanghai Advanced Research Institute; Chinese Academy of Sciences; Shanghai 201210 China
4. Department of Electronic and Computer Engineering; Hong Kong University of Science and Technology; Hong Kong China