LI Wenqiang1,2,3 , WU Min1,2,3 , LI Weijun1,2,3 , HAO Meilan1,2,3 , and YU Lina1,2,3** 1. AnnLab, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China 2. School of Electronic, Electrical and Communication Engineering & School of Integrated Circuits, University of Chinese Academy of Sciences, Beijing 100049, China 3. Beijing Key Laboratory of Semiconductor Neural Network Intelligent Sensing and Computing Technology, Beijing  100083, China