[1] Northwestern Polytech Univ Shenzhen, Res & Dev Inst, Shenzhen 518057, Peoples R China
[2] Northwestern Polytech Univ, Sch Phys Sci & Technol, Xiaan 710072, Peoples R China
[3] Inst Semicond, Chinese Acad Sci, Key Lab Semicond Mat Sci, Beijing 100083, Peoples R China
[4] Univ Chinese Acad Sci, Ctr Mat Sci & Optoelect Engn, Beijing 100049, Peoples R China
[5] Guangdong Acad Sci, Inst New Mat, Guangzhou 510650, Peoples R China
[6] Leibniz Inst Festkorper & Werkstoffforsch IFW Dres, D-01171 Dresden, Germany