1. School of Electronic and Computer EngineeringPeking University Shenzhen Graduate School Shenzhen 518055 P. R. China
2. Key Lab of Advanced Micro/Nano Electronic Devices & Smart Systems of ZhejiangCollege of Information Science and Electronic EngineeringZhejiang University Hangzhou 310027 P. R. China
3. State Key Laboratory of Optoelectronic Materials and TechnologiesSchool of Electronics and Information TechnologySun Yat‐Sen University Guangzhou 510006 P. R. China
4. National Center for Nanoscience & Technology Beijing 100190 P. R. China