1. Key Lab of Opto‐electronics Technology Ministry of Education College of Microelectronics Beijing University of Technology Beijing 100124 China
2. Key Laboratory of Nanodevices and Applications Suzhou Institute of Nano‐tech and Nano‐bionics Chinese Academy of Sciences Suzhou Jiangsu 215123 China
3. Nanchang Nano‐Devices and Technologies Division Suzhou Institute of Nano‐Tech and Nano‐Bionics Chinese Academy of Sciences Nanchang Jiangxi 330200 China