Defect-induced recombination analysis in 4H-SiC epitaxial layers based on detailed microwave photoconductive decay curve evaluation

Abstract

Evaluation of defect-related carrier lifetimes in 4H-SiC epitaxial layers is essential for assessing material quality and device performance. The microwave photoconductive decay (μ-PCD) method is widely used for wafer-level lifetime characterization; however, conventional evaluations based on a single lifetime value provide limited insight into defect-induced recombination behavior. In this study, μ-PCD decay curves were analyzed in detail for various defect types in 4H-SiC epitaxial layers to elucidate the impact of defect-induced recombination on excess carrier decay behavior. Polytype inclusions, micropipes, stacking faults, and propagated stacking faults were identified from 1/e lifetime images derived from μ-PCD measurement data. Decay curves acquired at each defect location were analyzed using a multi-component model to separately evaluate the high-intensity (early-time) and low-intensity (late-time) regions. Although all defects appeared as lifetime-reduced regions in 1/e lifetime images, the corresponding μ-PCD decay curves exhibited distinct decay characteristics. Polytype inclusions exhibited both a short-lifetime component consistent with enhanced recombination at the defect interface and a long-lifetime component associated with the defect bulk, whereas planar defects, such as stacking faults, were predominantly governed by short-lifetime interface-related recombination. Furthermore, mapping images that selectively highlighted polytype inclusions were successfully demonstrated by focusing on decay behavior within a specific time window. These results indicate that the temporal characteristics of μ-PCD signals contain physically meaningful information, reflecting both the recombination environment and the cross-sectional structure of epitaxial defects. The proposed analysis framework extends μ-PCD from a conventional lifetime evaluation technique to an advanced, defect-selective characterization method for 4H-SiC epitaxial layers.