1. Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low‐Dimensional Structural Physics and DevicesSchool of Physics and ElectronicsHunan University Changsha 410082 China
2. State Key Laboratory of Infrared PhysicsShanghai Institute of Technical PhysicsChinese Academy of Sciences Shanghai 200000 China
3. Department of Electronic and Computer EngineeringHong Kong University of Science and Technology Hong Kong SAR 999077 China
4. Department of Materials Science and EngineeringCity University of Hong Kong Tat Chee Avenue Kowloon Hong Kong SAR 999077 China