Theoretical insights into β-Ga2O3/diamond heterojunction interfaces: Surface selection, band alignment, and interfacial interaction

β-Ga2O3/diamond heterojunctions demonstrate considerable potential for applications in electronics and optoelectronics. However, theoretical investigations into their electrical properties remain largely unexplored. In this study, we provide a detailed examination of the electrical properties in β-Ga2O3/diamond heterojunctions with various experimentally reported surface combinations. All heterojunctions exhibit type-II band alignment, with valence band offsets (VBOs) ranging from 1.84 to 2.78 eV owing to material anisotropy and mismatch-induced strains. Furthermore, the influence of H-termination on the β-Ga2O3/diamond heterojunction was systematically investigated. Results indicate that H-termination significantly increases the VBOs by 1.11–1.88 eV while introducing a van der Waals barrier that impedes carrier transport. At covalent-bonded interfaces, band bending reduces the interface barrier, thereby facilitating carrier transport. Finally, the application prospects of these heterojunctions were comprehensively explored. This work offers theoretical insights for the co-design of β-Ga2O3/diamond heterojunctions.