Trade-off optimization of electrical performance and reliability in IGZO TFTs under light stress with Al2O3/ZrO2 bilayer dielectrics

Abstract

We report a comparative analysis of instability in In–Ga–Zn–O (IGZO) thin-film transistors (TFTs) incorporating various high-ĸ gate dielectrics under light illumination. For high resolution, low power display IGZO with high-ĸ oxide has received attention and shows enhanced electrical performance. But there is not enough study about illumination stress. Instability of TFTs at display can cause critical problems like color non-uniformity and blurring effects. A clear trade-off is observed between electrical performance and stability among devices with Al2O3, ZrO2, and HfO2 gate insulators. To mitigate the individual limitations of each oxide, an Al2O3/ZrO2 bilayer structure is implemented. The resulting bilayer IGZO TFTs exhibited better mobility and subthreshold swing about three times lower and a 12% decrease, respectively, compared to Al2O3 single-layer devices, while also demonstrating more than a 2 V improvement in breakdown voltage over HfO2- and ZrO2-based TFTs, along with enhanced stability under prolonged light exposure.