[1] Xiamen Univ, Dept Elect Sci, Fujian Engn Res Ctr Solid State Lighting, Xiamen 361005, Peoples R China
[2] Natl Chiao Tung Univ, Inst Electroopt Engn, Hsinchu 30010, Taiwan
[3] HKUST Fok Ying Tung Res Inst, Guangzhou 511458, Guangdong, Peoples R China
[4] Xiamen Univ, Dept Elect Engn, Xiamen 361005, Peoples R China