Unraveling the Defect Physics of SiC Micropipe Sidewalls by Non-Line-of-Sight Confocal Spectromicroscopy: Amphoteric Giant Traps

TL;DR

This study introduces a non-line-of-sight confocal spectromicroscopy technique to investigate the defect physics of SiC micropipe sidewalls, revealing their role as giant traps contributing to leakage current.

Contribution

The paper develops a novel optical method to analyze high-aspect-ratio defects and uncovers the amphoteric giant trap nature of micropipe sidewalls in SiC.

Findings

Micropipe sidewalls host high densities of deep-level donor and acceptor states.

Dominant DAP-like emission persists at room temperature across excitation powers.

Micropipe sidewalls act as extended traps facilitating trap-assisted leakage current.

Abstract

Micropipes are among the most detrimental defects in SiC wafer and are closely linked to catastrophic device failure. However, the microscopic defect nature of their internal sidewalls and the mechanism of the associated leakage current remain poorly understood, because their high-aspect-ratio geometry severely restricts direct optical probing. Here, we develop a non-line-of-sight confocal multiple-reflection spectromicroscopy technique combined with direct defect photoionization to unravel the defect physics of micropipe sidewalls. We show that these sidewalls host a high density of donor-like and acceptor-like deep-level states, giving rise to ultrabroad emission bands composed of intrinsic DAP-like recombination and detrapping-mediated free-to-bound transitions. Unlike conventional defect luminescence, the DAP-like emission remains dominant even at room temperature across all excitation powers. This behavior is attributed to rapid carrier capture by the sidewall defects, as evidenced by fast-rising and nanosecond-scale decay dynamics, along with coupled carrier kinetics. These results suggest that micropipe sidewalls can serve as extended amphoteric giant traps and carrier reservoirs, facilitating leakage current through trap-assisted transport. Our work provides a nondestructive optical approach for directly probing high-aspect-ratio extended defects and offers deep mechanistic insight into their defect physics and leakage mechanisms.