Effect of oxygen in the annealing treatment of Al2O3/β-Ga2O3 MOS capacitors

Abstract

Gallium oxide (Ga₂O₃) has emerged as a highly promising material for high-power electronic applications, owing to its ultra-wide bandgap, exceptional breakdown electric field, and low conduction losses. However, interfacial defects between Ga₂O₃ and the gate dielectric critically undermine device performance, highlighting the urgent need for robust interface engineering strategies. This study investigated the effect of annealing treatment on the interfacial and dielectric properties of Al₂O₃/β-Ga₂O₃ metal-oxide-semiconductor (MOS) capacitors. A comprehensive analysis of interface, border, and bulk traps revealed that O₂ annealing markedly improved both interface passivation and dielectric properties. The presence of active oxygen species promoted Ga–O bond formation, suppressing surface dangling bonds and oxygen vacancies, and thereby enabling the growth of a high-quality dielectric layer. In contrast, while N₂ annealing reduced surface contaminants, its lack of active oxygen species limited defect passivation. These results underscored the pivotal role of oxygen in thermal treatments and offered a practical route toward high-performance Ga₂O₃-based power devices.