[1] Hubei Normal Univ, Sch Mat Sci & Engn, Hubei Key Lab Photoelect Mat & Devices, Huangshi 435002, Peoples R China
[2] Hubei Normal Univ, Coll Phys & Elect Sci, Huangshi 435002, Peoples R China
[3] Nanjing Univ, Lab Solid State Microstruct, Nanjing 210093, Peoples R China
[4] Nanjing Forestry Univ, Dept Appl Phys, Coll Sci, Nanjing 210037, Peoples R China
[5] Southeast Univ, Minist Educ, Sch Phys, Key Lab Quantum Mat & Devices, Nanjing 211189, Peoples R China