1. Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, PR China
2. Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, PR China
3. School of Integrated Circuits, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, PR China