1. School of Electronic and Computer Engineering, Peking University Shenzhen Graduate School, Shenzhen, 518055, China
2. Department of Materials Science and Engineering, National Chung Hsing University, Taichung, 40227, Taiwan
3. Department of Physics, National Sun Yat-sen University, Kaohsiung 804, Taiwan
4. Institute of Materials and Optoelectronics, National Sun Yat-sen University, Kaohsiung 804, Taiwan