[1] Chinese Acad Sci, Inst Semicond, Nanooptoelect Lab, Beijing 100083, Peoples R China
[2] Chinese Acad Sci, Grad Univ, Beijing 100190, Peoples R China
[3] Lehigh Univ, Dept Elect & Comp Engn, Bethlehem, PA 18015 USA
[4] Tsinghua Univ, Dept Elect Engn, State Key Lab Integrated Optoelect, Beijing 100084, Peoples R China