1. Guangdong Engineering Research Center of Optoelectronic Functional Materials and Devices, College of Semiconductor Science and Technology, South China Normal University, Foshan 528225, People’s Republic of China
2. School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
3. Institute of Semiconductors, Guangdong Academy of Sciences, Guangzhou 510650, China