Performance enhancement of InSnZnO thin-film transistors by dual-active-layer architecture with various oxygen flow rates

Oxide thin film transistors (TFTs) have been one of the promising transistors in high-resolution displays. Unfortunately, their electrical performance, especially mobility, is limited by oxygen related defects in the active layers. Here, a homojunction dual-active-layer architecture using sputtering oxygen strategy is employed to enhance the electrical performance of InSnZnO (ITZO) TFTs. The ITZO dual active layers with varying oxygen contents are sequentially sputtered by adjusting the oxygen gas flow rate. The oxygen effects on the electrical performance of the ITZO TFTs are investigated. As the oxygen content increases, the mobility decreases while the threshold voltage increases. The dual-active-layer architecture, composed of ITZO films with varying oxygen contents, significantly improves the mobility. The dual-layer ITZO TFT shows excellent performance with a mobility of 50.51 ± 4.16 cm²/V·s, a subthreshold swing of 0.59 ± 0.19 V/dec, a threshold voltage of −0.77 ± 1.40 V, an off-state current of ∼10⁻¹² A, and an on/off-state current ratio of more than 10⁸. The gate bias stress stability of the ITZO TFTs is investigated. Under negative bias stress, the threshold voltage shift in single-layer TFTs improves from −14 to −8 V as the oxygen flow rate increases from 1 to 7 SCCM. The dual-layer TFTs show a reasonable threshold voltage shift under bias stress. This work demonstrates that the ITZO TFTs exhibit great potential for next-generation electronic applications.