1. State Key Laboratory on Integrated OptoelectronicsInstitute of SemiconductorsChinese Academy of Sciences Beijing 100083 P. R. China
2. College of Materials Science and Opto‐Electronic TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
3. Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic SystemsSchool of Materials Science and EngineeringBeijing Institute of Technology 100081 Beijing China