Nitrogen-enabled amorphous stabilization of high-mobility in-rich IGO via PEALD for uniform and reliable oxide TFTs

Abstract

Indium-based oxide semiconductors are promising materials for next-generation display backplanes owing to their high intrinsic carrier mobilities. However, their strong tendency to crystallize and excessive carrier generation often reduce the device uniformity and reliability. In this study, nitrogen-doped indium-rich indium gallium oxide (IGO) thin films were fabricated via plasma-enhanced atomic layer deposition (PEALD) using N2O plasma. Nitrogen incorporation effectively suppressed crystallization and passivated the oxygen vacancies, which produced stable amorphous films, even after annealing at 400 °C. The prepared IGO thin-film transistors (TFTs) exhibited a high mobility of 55.3 cm2/V·s, a normally off threshold voltage of 0.7 V, and a steep subthreshold swing of 85 mV/dec. Nitrogen doping increased the threshold voltage uniformity by 90% (standard deviation = 42 mV). Moreover, the bias-stress stability improved by 79% under positive bias temperature stress and 83% under negative bias temperature stress, with small shifts in the threshold voltage of 0.23 and 0.04 V, respectively. These improvements were attributed to the formation of a grain boundary-free amorphous network and the reduction of deep-level traps through controlled nitrogen doping. This study demonstrates that PEALD-based nitrogen incorporation offers a simple and scalable route for realizing high-mobility, uniform, and reliable amorphous oxide TFTs for future display technologies.