Improvement in the electrical properties of a-IGZO TFTs by using PA-PI as a modification layer

Abstract

High performance display requires thin film transistors (TFTs) to have better electrical characteristics. In this study, we used photoalignment polyimide (PA-PI) as the modification layer to modify the morphology of the insulating layer and improve the contact characteristics between the insulating layer and the active layer, so as to improve the electrical properties of amorphous Indium Gallium Zinc Oxide (a-IGZO) TFTs. The modified layer was prepared on the polymethylmethacrylate (PMMA) insulating layer and then irradiated with 254 nm UV polarized light. The anisotropy and surface morphology of the modified layer were investigated, and devices based on different insulating layer structures were prepared and tested. The typical device parameters of IGZO TFTs prepared under optimal conditions showed a high saturation mobility (μsat) of 9.68 cm2/V·s, the switching ratio was 1.01 × 105, the threshold voltage was 3.7 V, and the sub-threshold swing was 2.1 V/dec. The highest saturated carrier mobility μsat increased by 145% compared with PMMA single insulation layer devices.