Heterogeneous-Stack IGO/IZTO Thin Film Transistors: Guide to High Mobility and Enhanced Stability

Oxide thin film transistors (TFTs) have been widely adopted as pixel-switching and driving elements in commercial flat-panel displays. However, achieving high mobility is often severely restricted by instability issues, which primarily arise from the modulation of oxygen vacancy defect states within the channel. In this study, we demonstrate a heterogeneous-stack channel configuration based on IGO and IZTO thin films to realize high-mobility oxide TFTs with superior stability under gate-bias illumination stress. The front channel layer consists of IGO, which facilitates efficient charge transport due to its intrinsically high carrier concentration. Meanwhile, the back channel employs IZTO, whose wide bandgap effectively suppresses the ionization of oxygen vacancies and electronic transitions under illumination. Through strategic band alignment engineering within the heterogeneous-stack channel, the optimized IGO/IZTO TFT exhibits significantly enhanced electrical performance, including a mobility of 38.25 cm2 V–1 s–1, a subthreshold swing of 63.60 mV/dec, and a ratio of ON-state current to OFF-state current exceeding 5 × 107. Comprehensive electrical characterization, systematic stability tests, and spectroscopic analysis are conducted to elucidate the underlying mechanism responsible for the improved mobility and threshold voltage regulation. It is suggested that the quantum well formed at the heterointerface not only provides multiple conductive pathways but also traps photoionized electrons via Fermi-level engineering. This design strategy offers a promising approach to resolving the longstanding mobility–stability trade-off in oxide TFTs for high-end display applications.