1. School of Materials
and Energy, Guangdong University of Technology, Guangzhou, 510006 Guangdong, P. R. China
2. State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials Science & Engineering, Sun Yat-sen University, Guangzhou, 510275 Guangdong, P. R. China
3. Institute of Micro-Nano Optoelectronic Technology, Shenzhen Key Laboratory
of Micro-Nano Photonic Information Technology, College of Electronic
Science and Technology, Shenzhen University, Shenzhen, 518060 Guangdong, P. R. China
4. State Key Laboratory for Superlattices and Microstructures, Institute
of Semiconductors, Chinese Academy of Sciences, Beijing 100083, P. R. China