1. School of Electronic and Computer Engineering
2. Peking University
3. Shenzhen Graduate School
4. Shenzhen 518055
5. China
6. Department of Materials Science and Engineering
7. National Chung Hsing University
8. Taichung 40227
9. Taiwan
10. Department of Physics
11. National Sun Yat-sen University
12. Kaohsiung 804
13. Institute of Materials and Optoelectronics