First-principles study of oxygen vacancy defects in β-quartz SiO₂/Si interfaces

Abstract

Understanding the electronic structures of gate oxides in Si-based devices is significant for improving device performance. We investigate the electronic properties of the oxygen vacancy defects in β-quartz SiO2/Si interface structure using first-principles calculations. The results indicate that the constructed (SiO2)4/(Si)4 structure is an indirect-gap semiconductor, with its band edges contributed by Si side and a large band-edge energy difference (> 1.780 eV). Our study reveals that the presence of oxygen vacancy defects reduces the band gap, and VO1 is transformed from indirect into direct band gap. The Si dangling bonds in VO1 cause charge localization around the O vacancy, while the formation of Si-Si bonds in VO2 and VO3 lead to electron delocalization. In the calculation
of defect formation energies, we find that VO1 maintains the lowest formation energy across different states, making it more likely to form and structurally stable. Compared to O-rich environments, the formation energy in O-poor environments is overall reduced by approximately 4.5 eV, indicating that oxygen vacancy defects are more likely to form and be controlled under O-poor conditions. Our
study emphasizes the importance of interface structure and defect characteristics in semiconductor research, providing insights for the development of Si-based devices.