Mobility and current boosting of In-Ga-Zn-O thin-film transistors with metal capping layer oxidation

Abstract

This study investigates the effect of an oxidized Ta capping layer on the boosting of field-effect mobility (mu FE) of amorphous In-Ga-Zn-O (a-IGZO) Thin-film transistors (TFTs). The oxidation of Ta creates additional oxygen vacancies on the a-IGZO channel surface, leading to increased carrier density. We investigate the effect of increasing Ta coverage on threshold voltage (V th), on-state current, mu FE and gate bias stress stability of a-IGZO TFTs. A significant increase in mu FE of over 8 fold, from 16 cm2 Vs-1 to 140 cm2 Vs-1, was demonstrated with the Ta capping layer covering 90% of the channel surface. By partial leaving the a-IGZO uncovered at the contact region, a potential barrier region was created, maintaining the low off-state current and keeping the threshold voltage near 0 V, while the capped region operated as a carrier-boosted region, enhancing channel conduction. The results reported in this study present a novel methodology for realizing high-performance oxide semiconductor devices. The demonstrated approach holds promise for a wide range of next-generation device applications, offering new avenues for advancement in metal oxide semiconductor TFTs.