First-principles study of hole trapping at GaSb/AlSb heterointerfaces: Unveiling the role of orbital hybridization in Al-related defects

Antimony-based (Sb-based) short-wave infrared (SWIR) photodetectors have attracted considerable attention for their applications in non-destructive optical analysis. However, defect-induced charge trapping at heterojunction interfaces severely degrades device performance and stability, while the dominant defect types and their underlying physical mechanisms remain poorly understood. In this study, we employ first-principles calculations with Marcus charge transfer theory to investigate the defect-induced hole trapping process within the GaSb/AlSb heterojunction. We find that among all intrinsic defects examined, Sb vacancy (\rm V_\rm Sb), Al vacancy (\rm V_\rm Al), and the Al antisite on Sb (Al_\rm Sb) introduce shallow acceptor levels near the valence band maximum (VBM), rendering them highly effective in trapping holes. Moreover, we demonstrate that Al-related defects (\rm V_\rm Al and Al_\rm Sb) undergo substantial orbital hybridization with the VBM. This significantly enhances the coupling strength between the initial and final states, thereby boosting hole trapping efficiency. These findings provide crucial insights into the performance limitations of Sb-based SWIR photodetectors and offer valuable guidance for defect engineering and device optimization.