Enhanced Carrier Transport and Stability in Thin-Film Transistors Based on ITZO/IGZO Heterojunction Channel and Al₂O₃ Passivation

The mobility-stability trade-off in oxide semiconductor thin-film transistors (TFTs) limits their use in modern electronics, especially in display technologies. Here, we present high-performance ITZO/IGZO heterojunction TFTs with an Al2O3 passivation layer, achieving significant enhancements in both the stability and carrier transport. The formation of a two-dimensional electron gas (2DEG) at the heterointerface is found to significantly enhance the carrier transport, resulting in increased saturation mobility by up to 50% compared to single-channel ITZO TFTs. To address the negative threshold voltage due to increased carrier concentration associated with the 2DEG formation, an Al2O3 passivation layer is introduced to suppress channel defects, which successfully induces a positive shift in threshold voltage as well as further enhances electrical performance and stability. The optimized Al2O3-passivated ITZO/IGZO heterojunction TFTs exhibit a high saturation field-effect mobility of 48.34 ± 0.85 cm2/Vs, a positive threshold voltage of 0.56 ± 0.02 V, a low subthreshold swing of 59.96 ± 3.24 mV/dec, an on/off current ratio exceeding 108, and excellent operational stability. These findings suggest that ITZO/IGZO heterojunction TFTs with an Al2O3 passivation layer offer considerable potential for next-generation display applications and beyond, paving the way for enhanced performance in future electronic devices.