First Principles Study of the Stability and Diffusion Mechanism of a Carbon Vacancy in the Vicinity of a SiO₂/4H-SiC Interface

The carbon vacancy in bulk 4H.SiC and in the vicinity of an SiO₂/(0001).4H.SiC interface using density-functional theory is studied. It is found that the migration is hindered in the immediate vicinity of the interface, with the energy barrier for diffusion being ≈15% greater than the same defect in bulk 4H-SiC. Herein, it is shown that the increased barrier is a consequence of the stabilization of the vacancy in the immediate interface due to a combination of strengthened reconstructions and interfacial relaxation, coupled with the destabilization of the transition.state structure.