Improvement of electrical properties of ZnO TFT with NbLaO-based stacked gate dielectrics

Abstract

The double-stacked gate dielectrics (DSGD), which consisted of either NbLaO/Al2O3 or NbLaO/SiO2, were used to improve the electrical performance of zinc oxide thin-film transistor (ZnO-TFT) with single-layer NbLaO gate dielectric (SLGD). Compared to ZnO-TFT with SLGD, the ZnO-TFTs with DSGD exhibit better electrical performance, specifically for the device with the NbLaO/SiO2 DSGD, with an increase of the field-effect mobility from 5.77 cm2V[Formula: see text]s[Formula: see text] to 39.64 cm2V[Formula: see text]s[Formula: see text], an enhancement of the on/off current ratio by two orders of magnitude, a reduction of the subthreshold slope from 110 mV/decade to 70 mV/decade. The performance enhancements are attributed to a low root-mean-square surface roughness of less than 0.3 nm and a low trap-state density of less than [Formula: see text] cm[Formula: see text] (even [Formula: see text] cm[Formula: see text] for the NbLaO/SiO2 DSGD) in the bulk of the channel and at the ZnO/NbLaO interface. The results imply that ZnO-TFTs with DSGD have the potential for the application of high-resolution flat panel display.