Effect of simultaneous mechanical and electrical stress on the electrical performance of flexible In-Ga-Zn-O thin-film transistors

Abstract

We investigated the effect of simultaneous mechanical and electrical stress on the electrical characteristics of flexible indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs). The IGZO TFTs exhibited a threshold voltage shift (δVTH) under an application of positive-bias-stress (PBS), with a turnaround behavior from the positive δVTH to the negative δVTH with an increase in the PBS application time, whether a mechanical stress is applied or not. However, the magnitudes of PBS-induced δVTH in both the positive and negative directions exhibited significantly larger values when a flexible IGZO TFT was under mechanical-bending stress than when it was at the flat state. The observed phenomena were possibly attributed to the mechanical stress-induced interface trap generation and the enhanced hydrogen diffusion from atomic layer deposition-grown Al2O3 to IGZO under mechanical-bending stress during PBS. The subgap density of states was extracted before and after an application of PBS under both mechanical stress conditions. The obtained results in this study provided potent evidence supporting the mechanism suggested to explain the PBS-induced larger δVTHs in both directions under mechanical-bending stress.