1. State Key Laboratory for Supperlattices and Microstructures Institute of Semiconductors Chinese Academy of Science Beijing 100083 P. R. China
2. Key Laboratory of Semiconductor Materials Science Institute of Semiconductors Chinese Academy of Science Beijing 100083 P. R. China
3. State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Science Beijing 100083 P. R. China
4. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
5. State Key Laboratory of Integrated Optoelectronics College of Electronic Science and Engineering Jilin University Changchun 130012 P. R. China