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.