[1] Chinese Acad Sci, State Key Lab Superlattices & Microstruct, Inst Semicond, Beijing 100083, Peoples R China
[2] Univ Chinese Acad Sci, Coll Mat Sci & Optoelect Technol, Beijing 100083, Peoples R China
[3] Hunan Univ, Sch Phys & Elect, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China
[4] Henan Normal Univ, Dept Phys, Xinxiang 453007, Peoples R China
[5] Chinese Acad Sci, Natl Ctr Nanosci & Technol, Key Lab Nanosyst & Hierarch Fabricat, Beijing 100190, Peoples R China