Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083;
Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083;
Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083;
Department of Physics, Wuhan University, Wuhan 430072;
Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083;
Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083;