[1] Shandong Univ, Inst Novel Semicond, Jinan 250100, Peoples R China
[2] Shandong Univ, Shandong Technol Ctr Nanodevices & Integrat, Sch Microelect, Jinan 250100, Peoples R China
[3] Shandong Univ, State Key Lab Crystal Mat, Jinan 250100, Peoples R China
[4] Univ Manchester, Sch Elect & Elect Engn, Manchester M13 9PL, Lancs, England