1. Institute
of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China
2. State
Key Laboratory of Electronic Thin Film and Integrated Devices, School
of Microelectronics and Solid-State Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
3. Department
of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
4. Engineering
Research Center for Semiconductor Integrated Technology, Institute
of Semiconductors, Chinese Academy of Science, Beijing 100083, P. R. China