1 Department of Photonics & Institute of Electro-Optical Engineering, College of Electrical and Computer Engineering, Taiwan Yang Ming Chiao Tung University, Hsinchu 30010, China
2 International Ph.D. Program in Photonics (UST), College of Electrical and Computer Engineering, Taiwan Yang Ming Chiao Tung University, Hsinchu 30010, China
3 Department of Electronic Science, Fujian Engineering Research Center for Solid-State Lighting, Xiamen University, Xiamen 361005, China
4 School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
5 Research Center for Applied Sciences, Academia Sinica, Taipei 11529, China
6 Department of Materials Science and Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong, China
7 e-mail: wutingzhu@xmu.edu.cn
8 e-mail: hckuo@faculty.nctu.edu.tw