1. School of Microelectronics and Advanced Innovation Center for Big Data and Brain Computing, Beihang University, Beijing 100191, China
2. Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
3. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
4. Department of Electrical Engineering, University of California, Los Angeles, California 90095, United States