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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2509.19948 |
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Table of Contents:
- Semiconductor heterostructures capable of separating photogenerated electrons and holes have a wide range of optoelectronic applications, including photodetectors, solar cells, and photocatalysts. $β$-Ga$_2$O$_3$ and rutile GeO$_2$ are both ultrawide-bandgap semiconductors, with bandgaps of 4.85 eV and 4.68 eV, respectively. In this work, we employ first-principles calculations based on density functional theory to investigate the band alignment of the $β$-Ga$_2$O$_3$/rutile GeO$_2$ heterojunction and explore the effect of interfacial oxygen vacancy. Calculations using the PBE0 hybrid functional based on an interface model show that a type-II band alignment emerges at the $β$-Ga$_2$O$_3$/rutile GeO$_2$ interface, which facilitates the separation of photogenerated carriers. The valence band maximum of $β$-Ga$_2$O$_3$ lies 0.38 eV below that of rutile GeO$_2$, and its conduction band minimum lies 0.36 eV below. The presence of interfacial oxygen vacancy in the stable configuration leads to a reduction in the band offset. Our results suggest that the $β$-Ga$_2$O$_3$/rutile GeO$_2$ heterojunction holds significant promise for application in strictly solar-blind photodetectors.