Hydrogen-assisted removal of oxygen vacancies in β-Ga2O3

Abstract

Oxygen vacancies (VO) are intrinsic defects in β-Ga2O3 that significantly impact its device performance. These vacancies can donate electrons to the conduction band, leading to unintentional n-type conductivity in as-grown β-Ga2O3. In addition, VO associated localized states can act as electron traps, scatter free carriers, and consequently degrade carrier mobility and overall device performance. Therefore, removing VO is crucial for improving material properties, promoting the development of p-type β-Ga2O3 and optimizing device performance. Currently, traditional methods for VO treatment, such as oxygen plasma treatment and thermal annealing, are effective but have high energy consumption, which is detrimental to carbon neutrality goals. This study presents a method for enhancing the removal of VO via hydrogen doping. β-Ga2O3 thin films were grown under low-oxygen conditions using metal-organic chemical vapor deposition, followed by hydrogen pre-annealing. X-ray photoelectron spectroscopy and cathodoluminescence characterizations of films treated under different annealing conditions confirmed the effectiveness of hydrogen doping in promoting VO elimination. Furthermore, ultraviolet photodetectors were fabricated using these films, and the analysis of their dark-state decay times provided additional evidence for reduced VO concentrations. Theoretical calculations based on density functional theory using a revised PBE functional and the climbing image nudged elastic band method reveal that hydrogen incorporation induces charge redistribution, facilitating VO migration, thus enhancing defect control.