Unraveling the defect physics of SiC micropipe sidewalls by non-line-of-sight confocal spectromicroscopy: Amphoteric giant traps

Abstract

Despite substantial advances in SiC crystal growth, micropipes can still occur in thick and large-diameter SiC wafers, remaining among the most detrimental extended defects associated with device failure. However, the microscopic nature of the defects residing on their internal sidewalls and their contribution to the leakage current remain poorly understood because the high-aspect-ratio hollow geometry severely restricts direct, nondestructive optical access. Here, we develop a non-line-of-sight confocal multiple-reflection spectromicroscopy combined with direct defect photoionization to unravel the underlying defect physics of micropipe sidewalls. We show that the internal sidewalls host a high density of spatially and energetically distributed donor-like and acceptor-like deep-level states, thus giving rise to ultrabroad defect emissions comprising inherent donor–acceptor-pair-like (DAP-like) recombination and detrapping-mediated free-to-bound transitions. The dominant DAP-like emissions can be attributed to rapid carrier capture by the sidewall defects, as evidenced by a fast rise, nanosecond-scale decay, and coupled carrier kinetics. These results suggest that micropipe sidewalls can serve as extended amphoteric giant traps and carrier reservoirs, providing preferential leakage pathways through trap-assisted carrier transport along the internal sidewalls. Our work establishes a nondestructive optical technique for directly probing high-aspect-ratio extended defects and provides mechanistic insight into their defect physics and associated leakage mechanisms.