1. School of Physics and Electronics Engineering
2. Zhengzhou University of Light Industry
3. Zhengzhou 453002
4. China
5. State Key Laboratory for Superlattices and Microstructures
6. College of Physics and Engineering
7. Henan University of Science and Technology
8. Luoyang 471023
9. Institute of Semiconductors
10. University of Chinese Academy of Sciences
11. Chinese Academy of Sciences
12. Beijing 100083