1 Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
2 Department of Electronic Science, Fujian Engineering Research Center for Solid-State Lighting, Xiamen University, Xiamen 361005, China
3 e-mail: wutingzhu@xmu.edu.cn
4 Institute of Photonics System, National Chiao Tung University, Tainan 71150, Taiwan
5 HKUST Fok Ying Tung Research Institute, Nansha District, Guangzhou 511458, China
6 Department of Electrical Engineering and Computer Sciences and TBSI, University of California at Berkeley, Berkeley, California 94720, USA
7 e-mail: hckuo@faculty.nctu.edu.tw