Solution-Processed Yttrium-Doped IZTO Semiconductors for High-Stability Thin Film Transistor Applications

In this article, solution-processed zinc-tin-oxide (ZTO), indium-zinc-tin-oxide (IZTO), and yttrium-doped indium-zinc-tin-oxide (IZTO:Y) thin film transistors (TFTs) were investigated. The results indicate that the field effect mobility of the ZTO TFTs is enhanced by indium doping, whereas leading to the degradation of stability. Y-doping IZTO TFTs were also studied aiming to improve the stability of IZTO TFTs. The IZTO:Y shows a relatively higher transmittance in the visible light region compared to the nondoped IZTO, which could be due to the decrease of shallow defect levels caused by oxygen vacancy in the bandgap. Based on the X-ray photoelectron spectroscopy analysis, the oxygen vacancy concentration of IZTO:Y thin films decreases dramatically from 36.5% to 18.5% with Y incorporation. Moreover, the stability of IZTO:Y TFTs under positive bias stress (PBS) is also significantly improved. The device with 5-mol% Y element shows a low threshold voltage shift of 0.7 V compared to 2.6 V of IZTO TFT. The improvement in stability and electrical properties of IZTO TFTs are attributed to the Y doping, which can suppress the oxygen vacancy defects. Therefore, the high stability and excellent electrical performance of Y-doped IZTO TFTs have shown great application potential in transparent devices.