Decoupled Dielectric Optimization and YbOx Contact Engineering in All-Spray-Processed Oxide Thin-Film Transistors

Abstract

Control of dielectric transport and contact energetics remains a central challenge in scalable oxide electronics. We present a decoupled optimization strategy for fully spray-processed oxide thin-film transistors with In₂O₃:W channels, where dielectric densification and interfacial dipole formation are engineered independently. MgO gate dielectrics reveal a transition from trap-assisted to Schottky-dominated leakage with increasing deposition temperature, suppressing defect-mediated conduction and reducing interface trap density. Transistors incorporating MgO deposited at 400°C exhibit improved electrostatic control, with electron mobility approaching 40 cm² V⁻¹ s⁻¹ and subthreshold swing reduced to 0.35 V dec⁻¹. Introduction of a thermochemically stabilized 3 nm YbO_x interlayer between the source/drain electrodes and the In₂O₃:W channel enhances operation. Kelvin probe measurements reveal a dipole-induced work-function reduction exceeding 1.7 eV. This band-alignment engineering lowers the injection barrier and suppresses contact limitations, enabling a transition from injection-limited toward channel-dominated transport. Consequently, fully spray-processed transistors exhibit electron mobility of 94 cm² V⁻¹ s⁻¹, subthreshold swing of 191 mV dec⁻¹, and on/off current modulation ratios exceeding 10⁷. Statistical analysis of 104 devices with identical nominal geometry further demonstrates the reproducibility of the optimized transistor characteristics across the evaluated device population. These findings establish a scalable route toward high-performance solution-processed electronics.