Engineered interface states and optical absorption of β-Ga2O3/4H-SiC heterojunctions by irradiation-induced oxygen defects from first-principles

Abstract

Designing high-performance β-Ga₂O₃/4H-SiC heterojunctions has been widely investigated in recent years due to their unique applications in photodetectors. Due to the low defect formation energy of oxygen vacancies, β-Ga₂O₃-based heterojunction photodetectors inevitably produce defects internally upon irradiaion accompanied by performance degradation, yet the underlying physics still remains elusive. Herein, we focus on investigating the influence of oxygen vacancy defects on electronic, optical and carrier transport properties of β-Ga₂O₃/4H-SiC heterojunctions to understand such degradation mechanisms using first-principles calculations. Our findings indicate that the irradiation-induced oxygen vacancies can significantly reduce the space charge region width of the heterojunction but slightly affect the electrostatic potential. When oxygen vacancies appear at the heterojunction boundary (β-Ga₂O₃ side), the bandgaps of both β-Ga₂O₃ and 4H-SiC decrease simultaneously. The interface states emerge when oxygen vacancies occur at the interface but do not affect the bandgaps. In addition, the oxygen vacancies could increase the optical absorption in the visible and ultraviolet bands, leading to more electron–hole pairs being quickly separated through the built-in electric field. Our calculations reveal the oxygen vacancy influence on the β-Ga₂O₃/4H-SiC heterojunction, which is helpful for analyzing photodetector failures and improving their performances.