<i>In-situ</i> sulfur anion doping for defect passivation and stability enhancement in ZnSnO thin-film transistors

Abstract Metal oxide thin-film transistors (TFTs) have garnered considerable attention as promising alternatives to liquid-crystal displays and organic light-emitting diode displays. Among different metal oxide semiconductors, zinc tin oxide (ZnSnO, ZTO) stands out as a promising option owing to its environmental friendliness, affordability, and suitability for low-temperature fabrication. Nevertheless, pristine ZTO TFTs exhibit considerable drawbacks in both performance and reliability, particularly when exposed to negative bias illumination (NBIS) and thermal stress, leading to pronounced threshold voltage variations. Here, we report an in-situ sulfur anion doping strategy to modulate the defect landscape of ZTO, yielding high-performance and highly stable S-doped ZTO (S-ZTO) TFTs. The incorporation of S anion at oxygen lattice sites effectively suppresses oxygen-vacancy–related trap states, leading to marked improvements in both carrier transport and operational stability. The optimized S-ZTO TFT (10 at% S) exhibits a field-effect mobility of 12.7 cm 2 (V·s -1 , a threshold voltage of 3.8 V, a subthreshold swing of 0.31 V dec −1 , and an ultralow leakage current of 7 × 10 −12 A. More importantly, in-situ sulfur incorporation significantly mitigates threshold voltage shifts under prolonged positive bias, NBIS, and thermal stress, outperforming pristine ZTO devices. This work demonstrates that in-situ sulfur doping offers a practical route to high-performance ZTO-based oxide TFTs that meet the reliability requirements of AMOLED and AM-LCD backplanes.

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