1. Institute of Microelectronics & Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan, Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan, Department of Electrical Engineering, Kun Shan University, Tainan 701, Taiwan, and Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan