1. College of Electron and Information Engineering, Key Laboratory of Digital Medical Engineering of Hebei Province, Key Laboratory of Optoelectronic Information Materials of Hebei Province, Hebei University, Baoding 071002, P. R. China
2. Department of Materials Science and Engineering, National University of Singapore, Singapore 117576, Singapore
3. Department of Electrical and Computer Engineering, Southern Illinois University Carbondale, Carbondale, Illinois 47901, United States
4. State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
5. Key Laboratory of Microelectronic Devices and Integrated Technology, Institute of Microelectronics Chinese Academy of Sciences, Beijing 100029, P. R. China