1. Semiconductor Research Center, Hon Hai Research Institute, Taipei 11492, Taiwan
2. Department of Electrophysics, College of Science, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
3. Department of Photonics, Institute of Electro-Optical Engineering, College of Electrical and Computer Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
4. Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan