1. Key Laboratory of Materials Physics of Ministry of Education
2. Department of Physics and Engineering
3. Zhengzhou University
4. Zhengzhou 450052
5. China
6. State Key Laboratory on Integrated Optoelectronics
7. College of Electronic Science and Engineering
8. Jilin University
9. Changchun 130012
10. Department of Materials Science
11. Fudan University
12. Shanghai 200433