1. Institute of Microelectronics Peking University Beijing 100871 P. R. China
2. Advanced Institute of Information Technology Peking University Hangzhou 311215 P. R. China
3. Innovation Center for Microelectronics and Integrated System Peking University Beijing 100871 P. R. China
4. Frontiers science center for nano‐optoelectronics Peking University Beijing 100871 P. R. China