Effects of Ta incorporation in La{sub 2}O{sub 3} gate dielectric of InGaZnO thin-film transistor

The effects of Ta incorporation in La{sub 2}O{sub 3} gate dielectric of amorphous InGaZnO thin-film transistor are investigated. Since the Ta incorporation is found to effectively enhance the moisture resistance of the La{sub 2}O{sub 3} film and thus suppress the formation of La(OH){sub 3}, both the dielectric roughness and trap density at/near the InGaZnO/dielectric interface can be reduced, resulting in a significant improvement in the electrical characteristics of transistor. Among the samples with different Ta contents, the one with a Ta/(Ta + La) atomic ratio of 21.7% exhibits the best performance, including high saturation carrier mobility of 23.4 cm{sup 2}/V·s, small subthreshold swing of 0.177 V/dec, and negligible hysteresis. Nevertheless, excessive incorporation of Ta can degrade the device characteristics due to newly generated Ta-related traps.