[1] Hunan Univ, Coll Elect & Informat Engn, Changsha 410082, Peoples R China
[2] Hunan Univ, Minist Educ, Engn Res Ctr Adv Semicond Technol & Applicat, Changsha 410082, Peoples R China
[3] CRRC Zhuzhou Elect Locomot Inst Co Ltd, Zhuzhou 412000, Peoples R China