[1] Fudan Univ, Dept Mat Sci, State Key Lab ASIC & Syst, Shanghai 200433, Peoples R China
[2] CALTECH, Dept Med Engn, Div Engn & Appl Sci, Pasadena, CA 91125 USA
[3] Northeastern Univ, Dept Elect & Comp Engn, Boston, MA 02115 USA
[4] Univ Elect Sci & Technol China, State Key Lab Elect Thin Films & Integrated Devic, Chengdu 610054, Peoples R China
[5] Chinese Acad Sci, State Key Lab Superlattices & Microstruct, Inst Semicond, Beijing 100083, Peoples R China