Unraveling the Impact of Cation Composition on Atomic Layer Deposited Ultrathin In–Sn–O Field-Effect Transistors

This article explores the optimization of Sn doping in ultrathin In₂O₃ field-effect transistors (FETs) to enhance their electrical performance and stability for next-generation semiconductor applications. Using plasma-enhanced atomic layer deposition (PEALD) at $150~^{\circ }$ C, indium tin oxide (ITO) films were fabricated with varying Sn concentrations. Through various analyses, we confirmed that Sn doping increased carrier density and effectively reduced oxygen vacancies, enhancing electrical conductivity. In addition, we confirmed that the optimal Sn doping level (12 at%) promoted preferential crystallization along the (222) direction, as observed in both 3-nm and 2-nm-thick films. The resulting ITO FETs demonstrated superior electrical performance, exhibiting a high field-effect mobility of $54.6~\pm ~0.61$ cm²/ $\text {V} \cdot \text {s}$ , a subthreshold swing (SS) of $99.8~\pm ~0.98$ mV/dec, and a threshold voltage of $0.34~\pm ~0.02$ V. Furthermore, the ITO FETs showed enhanced stability under bias-temperature stress conditions, outperforming conventional In₂O₃ FETs. This study highlights the potential of Sn-doped ITO channels in achieving high-performance, reliable ultrathin FETs for advanced memory and electronic applications.