1. Academy for Engineering and Technology, Engineering Research Center of Advanced Lighting Technology Fudan University Shanghai 200433 China
2. College of Electronic and Optical Engineering Nanjing University of Posts and Telecommunications Nanjing 210023 China
3. Shenzhen Institute of Wide-Bandgap Semiconductors Shenzhen 518055 China
4. Department of Microelectronics Delft University of Technology Delft 2628 CD Netherlands