1. School of Microelectronics, Southern University of Science and Technology, Shenzhen 518055, China
2. Department of Electric and Electronics Engineering, Southern University of Science and Technology, Shenzhen 518055, China
3. Harbin Institute of Technology, Harbin 150001, China
4. Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Hong Kong 0000, China
5. Department of Microelectronics, Delft University of Technology, Delft 2600 GB, Netherlands
6. Department of Materials Engineering, the University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
7. GaN Device Engineering Technology Research Center of Guangdong, Southern University of Science and Technology, Shenzhen 518055, China
8. The Key Laboratory of the Third Generation Semiconductors, Southern University of Science and Technology, Shenzhen 518055, China