1. School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
2. School of Physics and Engineering, Xingyi Normal University for Nationalities, Xingyi 562400, China
3. Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 2601, Australia
4. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
5. Grünberg Research Centre, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
6. Collaborative Innovation Center of Solid-State Lighting and Energy-Saving Electronics, Nanjing University, Nanjing 210093, China