1. GaN Optoelectronic Integration International Cooperation Joint Laboratory of Jiangsu Province, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
2. Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Kowloon 999077, Hong Kong
3. Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan
4. National Center for International Joint Research of Electronic Materials and Systems, School of Electrical and Information Engineering, Zhengzhou University, Zhengzhou 450001, China