1. Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
2. National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
3. School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
4. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
5. National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China