1. Department of Physics, National Sun Yat-sen University, 70 Lien-hai Road, Kaohsiung 80424, Taiwan
2. Advanced Optoelectronics Technology Center, National Cheng Kung University, Tainan 701, Taiwan
3. Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
4. Department of Photonics, National Sun Yat-Sen University, 70 Lien-hai Road, Kaohsiung 80424, Taiwan
5. Device Department, United Microelectronics Corporation, Tainan Science Park, Tainan 701, Taiwan