Charge-trapping dynamics and bias-stress stability in indium–tungsten oxide thin-film transistors under low thermal budget processing

Understanding and controlling charge trapping is critical for achieving reliable operation of amorphous oxide semiconductor thin-film transistors (TFTs), particularly under low thermal budget conditions where defect states are not fully passivated. In this work, we investigate the charge-trapping dynamics and bias-stress stability of indium–tungsten oxide (IWO) TFTs processed at temperatures ≤ 300 °C, with an emphasis on the relationship between defect states and device reliability. Systematic bias-stress measurements reveal that IWO TFTs exhibit significantly reduced threshold-voltage shifts (ΔVth) under both positive and negative gate bias stress, accompanied by longer charge-trapping time constants (τ) and lower effective trap density (Dit) compared with conventional amorphous oxide counterparts. The stretched-exponential analysis indicates slower carrier trapping kinetics in IWO, suggesting suppressed defect activation and reduced trap-assisted charge capture. These improvements are consistent with a more stable oxygen-bonding and defect environment; the specific role of strong W–O bonding is supported by prior literature, which mitigates the formation of oxygen-vacancy-related defect states and stabilizes the amorphous structure under thermally constrained processing conditions. In addition, long-term environmental measurements demonstrate minimal degradation in electrical characteristics over extended ambient exposure, supporting the enhanced long-term environmental stability of IWO under unpassivated conditions. The results establish a direct correlation between defect-state suppression and enhanced bias-stress reliability, providing a materials-physics framework for designing oxide TFTs with improved stability under low thermal budget processing.