The Influences of Oxygen Incorporation on the Defect Trap States of a-IGZO Thin-film Transistors

Thin-film transistors (TFTs) comprised of amorphous indium-gallium-zinc-oxide (a-IGZO) as the active channel layers were prepared by sputtering process at various Ar/O-2 gas flow ratios and their electrical properties were investigated. Device characterizations indicated that the TFT sample prepared at the condition of Ar/O2 ratio = 20:0.6 exhibits the best performance with field-effect mobility (mu(FE)) = 5.2 cm(2).V-1.sec(-1), threshold voltage (Vth) = 0.7 V, subthreshold gate swing (S.S.) = 0.9 V.decade(-1) and on/off ratio = 5x10(6). Such a sample also exhibited the lowest interface trap density (D-it = 2.8x10(10) eV(-1).cm(-2)) and the highest capacitance density (334 nF.cm(-2)) as revealed by capacitance-voltage (C-V) analysis and the lowest leakage current density of 25 nA/cm(2) at 10 MV/cm (in case of positive bias on top electrode) as revealed by current-voltage (I-V) measurement.