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 ( μ 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, μ FE and gate bias stress stability of a-IGZO TFTs. A significant increase in μ FE of over 8 fold, from 16 cm 2 Vs −1 to 140 cm 2 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.