1. School of Materials and EnergyGuangdong University of Technology Guangdong Guangzhou 510006 P. R. China
2. Department of Electronic EngineeringThe Chinese University of Hong Kong Hong Kong SAR Kowloon 999077 P. R. China
3. State Key Laboratory of Optoelectronic Materials and TechnologiesNanotechnology Research CenterSchool of Materials Science & EngineeringSun Yat‐Sen University Guangdong Guangzhou 510275 P. R. China
4. State Key Laboratory for Superlattices and MicrostructuresInstitute of SemiconductorsChinese Academy of Sciences Beijing 100083 P. R. China
5. Institute of SemiconductorsSouth China Normal University Guangdong Guangzhou 510631 P. R. China