1. Key Laboratory of Semiconductor Materials Science; Institute of Semiconductors; Chinese Academy of Sciences; Beijing 100083 P.R. China
2. School of Electronic Engineering; Xi′an University of Posts & Telecommunications; Xi′an P.R. China
3. ISCAS-XJTU Joint Laboratory of Functional Materials and Devices for Informatics; Beijing 100083 P.R. China
4. Beijing Huajin Chuangwei Technology Co., Ltd.; Beijing P.R. China