1. Fujian Key Laboratory of Semiconductor Materials and Applications, Department of Physics, Xiamen University, Xiamen 361005, China
2. Xiamen Industrial & Commercial School, Jimei district, Xiamen 361024, China
3. Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan