Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen 361005;
Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors,Chinese Academy of Sciences, Beijing 100083;
Department of Physics, Xiamen University, Xiamen 361005;
Department of Electronic Engineering, Xiamen University, Xiamen 361005;
Department of Electronic Engineering, Xiamen University, Xiamen 361005;
Department of Electronic Engineering, Xiamen University, Xiamen 361005;