Defect-Passivated InGaZnO/In2O3 Stacked Thin-Film Transistor with Visible-Light-Assisted Recovery for Room-Temperature ppb-Level NO₂ Detection

Abstract

The hierarchical stacking of oxide semiconductors presents a transformative strategy to address intrinsic defect limitations in amorphous metal oxide semiconductor (MOS)-based thin-film transistors (TFTs). Although conventional MOS-TFTs suffer from high defect densities that degrade carrier mobility and operational stability, the engineered stacking of InGaZnO (IGZO)/In2O3 bilayer TFTs demonstrates synergistic electrical and gas sensing enhancements. Fabricated via room-temperature RF magnetron sputtering, the IGZO/In2O3 TFTs exhibit superior electrical performance, including a near-zero threshold voltage (≈0 V), enhanced output current density, and reduced hysteresis, which is attributed to the defect passivation mechanism at the interface. These advancements enable low-power, high-stability gas sensors with amplified response signals. Crucially, the IGZO/In2O3 TFTs enable dual-mode optical recovery. Visible-light activation replaces UV irradiation, and achieves efficient sensor recovery while maintaining safety and energy efficiency, something unattainable with single-layer In2O3 TFTs. The stacked layers further ensure exceptional NO₂ selectivity towards 50 ppb detection across 25–100 °C and long-term stability, outperforming conventional high-temperature operating MOS gas sensors. By integrating defect-passivated interfaces, scalable TFT fabrication, and optical recovery compatibility, this work establishes IGZO/In2O3 stacked structure as a versatile platform for next-generation wearable and IoT-compatible gas sensing systems.