Comparative Study of Nb2O5, NbLaO, and La2O3 as Gate Dielectric of InGaZnO Thin-Film Transistor

Abstract

An amorphous InGaZnO thin-film transistor with high-k Nb2O5 as gate dielectric is prepared for the first time, showing typical field-effect characteristics with a saturation mobility of 2.3 cm2V-1s-1. By adding La in the Nb2O5 gate dielectric, the electrical performance of the device is significantly improved, because La incorporation can decrease the Nb2O5/InGaZnO interface roughness and passivate the defect states at/near the interface. Consequently, the sample with appropriate La content has a high saturation mobility of 28 cm2V-1s-1, a low threshold voltage of 1.84 V, a small subthreshold swing of 0.17 V/decade, and negligible hysteresis. However, the electrical performance of the sample with pure La2O3 as gate dielectric is inferior due to the hygroscopic nature of the La2O3 film, resulting in a rougher gate-dielectric/InGaZnO interface.