Decoupled Dielectric Optimization and YbO _x 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 In ₂ O ₃ :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 cm ² 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 In ₂ O ₃ :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 cm ² V ⁻¹ s ⁻¹ , subthreshold swing of 191 mV dec ⁻¹ , and on/off current modulation ratios exceeding 10 ⁷ . 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.