1. National-Local Joint Engineering Laboratory of New Energy Photovoltaic Devices; Key Laboratory of Digital Medical Engineering of Hebei Province; College of Electron and Information Engineering; Hebei University; Baoding 071002 P. R. China
2. Department of Materials Science and Engineering; National University of Singapore; Singapore 117576 Singapore
3. State Key Laboratory of ASIC and System; School of Microelectronics; Fudan University; Shanghai 200433 China
4. Key Laboratory of Microelectronic Devices & Integrated Technology; Institute of Microelectronics; Chinese Academy of Sciences; Beijing 100029 P. R. China
5. Electrical and Computer Engineering Department; Southern Illinois University Carbondale, Illinois; 1230 Lincoln Drive Carbondale IL 62901 USA
6. Institute of Microelectronics; Tsinghua University; Beijing 100084 China