1. Henan Key Laboratory of Photovoltaic Materials School of Physics Henan Normal University Xinxiang 453007 China
2. State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences & Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100083 China
3. State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics Peking University Beijing 100871 China
4. Henan Key Laboratory of Infrared Materials & Spectrum Measures and Applications Henan Normal University Xinxiang 453007 China