1. National Laboratory of Solid State Microstructures; School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures; Nanjing University; Nanjing 210093 P. R. China
2. Institute of High Performance Computing; 1 Fusionopolis Way 138632 Singapore
3. Department of Electronic Engineering and Materials Science and Technology Research Center; The Chinese University of Hong Kong; Hong Kong SAR P. R. China