1. State Key Laboratory for Superlattices and Microstructures, Chinese Academy of Sciences, Beijing 100083, China
2. School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, USA
3. State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
4. Zhejiang Provincial Key Laboratory of Solid State Optoelectronic Devices, Zhejiang Normal University, Jinhua 321004, China