How do oxygen vacancies affect carrier transport and interface states in β-Ga2O3/4H-SiC heterojunction photodetectors at elevated temperatures?

Abstract

Owing to their excellent optoelectronic and electrical properties, β-Ga₂O₃/4H-SiC heterojunctions have been widely employed to build solar-blind photodetectors. When photodetectors are used in extreme space environments, they suffer from high-energy proton, electron, X-ray, gamma ray and neutron irradiations. Thus, oxygen vacancies are inevitably created inside the heterojunction. In addition, the temperature of photodetectors in satellites rises under harsh operating conditions. Herein, we systematically evaluate the coupling effect of temperature and oxygen vacancies on carrier transport and interface states of β-Ga₂O₃/4H-SiC heterojunction photodetectors at the atomistic scale using first-principles calculations. Our results show that oxygen vacancies at the boundary considerably affect the bandgap of heterojunctions, while the interface oxygen vacancies would give rise to gap states. For the β-Ga₂O₃/4H-SiC heterojunction containing boundary oxygen vacancies, the effects of temperature and oxygen vacancies inhibit each other, leading to an increase in the bandgap of the β-Ga₂O₃ side. The high temperature and the creation of oxygen vacancies both reduce the width of the space charge region. The energy range and density of the interface states in heterojunctions containing interfacial oxygen vacancies increase with temperature. This study aims to understand the electron–phonon-oxygen vacancy coupling effects on β-Ga₂O₃/4H-SiC heterojunctions, which can benefit the design of high-performance photodetectors.