[1] Hebei Univ Technol, Sch Elect & Informat Engn, Key Lab Elect Mat & Devices Tianjin, Tianjin 300401, Peoples R China
[2] Chinese Acad Sci, Semicond Lighting R&D Ctr, Inst Semicond, Beijing 100083, Peoples R China
[3] Univ Chinese Acad Sci, Ctr Mat Sci & Optoelect Engn, Beijing 100049, Peoples R China
[4] Chinese Acad Sci, Inst Semicond, State Key Lab Superlattices & Microstruct, Beijing 100083, Peoples R China