we utilized hybrid density functional theory to study isolated interstitial point defects, and complexes of Si, in the low-symmetric monoclinic phase of Ga2O3. Defects in the crystal structure can significantly affect the performance and reliability of devices based on Ga2O3. Theoretical calculations indicate that while isolated interstitial Si is unlikely to occur under equilibrium conditions, its stabilization through interaction with Ga vacancies provides a realistic pathway for maintaining n-type conductivity in non-equilibrium environments.
Our key findings on isolated defects indicates:
· Substitutional SiGaI in β-Ga₂O₃ acts as a shallow donor, shifting the Fermi level into the conduction band without forming localized gap states. Its Bader charge of +3.12 e is consistent with the experimentally observed +4 oxidation state, confirming its donor nature.
· In contrast, the isolated interstitial Sii9 possesses a much smaller Bader charge (+2.04 e) and introduces a mid-gap defect band. Coupled with its high formation energy, this indicates that it is not a stable or efficient donor species.
And our analysis of stabilized complexes reveals:
· When Si interacts with nearby Ga vacancies, forming Sii9–1VGaI and Sii9–2VGaI complexes, the electronic structure and optical response are modified:
· The Sii9–1VGaI complex successfully retains n-type character (shallow donor) and exhibits a red-shifted optical edge.
· The Sii9–2VGaI complex introduces deep localized states in the conduction band and lowers the absorption edge below 4 eV.
· The comparable Bader charge of Si in Sii9–1VGaI (+3.08 e), and Sii9–2VGaI (+3.04 e) to that of SiGaI, along with the calculated negative formation energy, strongly suggests that these complexes can coexist with substitutional donors under implantation conditions.
