1. Department of Photonics and Institute of Electro-Optical Engineering, National Chiao-Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan
2. Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan
3. Research and Development Center, Epistar Corp., 21, Li-Hsin Rd., Hsinchu Science Park, Hsinchu 300, Taiwan
4. Department of Electronic Engineering and Institute of Electronics Engineering, Chang Gung University, Taoyuan 33302, Taiwan
5. Department of Radiation Oncology, Chang Gung Memorial Hospital, Linkou 33305, Taiwan