1. Guangdong Provincial Engineering Laboratory for Wide Bandgap Semiconductor Materials and Devices School of Electronics and Information Engineering South China University of Technology Guangzhou 510640 China
2. Engineering Research Centre for Optoelectronics of Guangdong Province School of Physics and Optoelectronics South China University of Technology Guangzhou 510640 China
3. School of Physical Science and Technology Guangxi University Nanning 530004 China
4. Zhongshan Institute of Modern Industrial Technology South China University of Technology Zhonghan 528437 China