Geometrically designed amorphous oxide semiconductor heterojunction thin-film transistors for enhanced electrical performance and stability

We report the geometrical design of indium-zinc-tin-oxide/zinc-tin-oxide (IZTO/TZO) heterojunction thin-film transistors (TFTs) to achieve high electrical performance and stability. The coverage ratio of the IZTO front-channel-layer (FCL) in the channel region was varied to investigate its impact on electrical properties such as field-effect mobility and bias stability. We observed that with a 90% coverage ratio of IZTO FCL, the mobility increased from 15.9 cm 2 Vs −1 to 20.4 cm 2 Vs −1 , with a suppressed threshold voltage ( V th ) shift. The IZTO/ZTO TFTs exhibited improved positive gate-bias stability showing a V th shift of +2.46 V. The band bending occurring at the heterointerface is attributed to the enhanced electrical performance.