1. State Key Laboratory of Integrated OptoelectronicsInstitute of SemiconductorsChinese Academy of Sciences No. A35, Qinghua East Road, Haidian District Beijing 100083 China
2. Center of Materials Science and Optoelectronic EngineeringUniversity of Chinese Academy of Sciences No. 19A, Yuquan Road, Shijingshan District Beijing 100049 China
3. School of Materials Science and EngineeringUniversity of Shanghai for Science and Technology No. 516, Jungong Road Shanghai 200093 China