The impact of composite defects Vⁱ _O(Ga) on the electrical properties of <i>β</i>-Ga₂O₃/AlN heterojunctions

Abstract Due to inherent lattice and thermal mismatch, AlN/ β -Ga 2 O 3 interfaces inevitably contain defects. This paper employs density functional theory (DFT) to systematically investigate the electronic properties of ideal and defect-containing interfaces, specifically those with O–Al (V i O ), O–N (V i O ), and Ga–N (V i Ga ) defects. The results indicate that the inclusion of composite defects alters the interface structure. This alteration is most pronounced at the O–N (V i O ) interface. Based on the analysis of formation and binding energies, composite defects are found to be more readily formed than single-point defects. Among these, the O–Al (V i O ) interface is the most likely to form, while the Ga–N (V i Ga ) interface proves to be the most stable. Compared to AlN, the defect levels within the bandgap are primarily influenced by atoms on the β -Ga 2 O 3 side. Charge analysis indicates that charge transfer from AlN to β -Ga 2 O 3 is observed across all interfaces, creating an internal electric field. Notably, the ideal O–N interface demonstrates the highest charge transfer capability, which facilitates the formation of a high-density two-dimensional electron gas (2DEG). Compared to other composite defect models, the O–N (V i O ) heterojunction model exhibits the most significant reduction in potential difference relative to the ideal interface. Composite defects significantly lower the 2DEG density; therefore, controlling defects during the preparation process is crucial for balancing device stability and 2DEG density. These findings provide critical insights for optimizing the electronic properties of β -Ga 2 O 3 /AlN heterostructures and for the design of high-performance high-electron-mobility transistor devices.