The influence of structural defects upon carrier lifetimes in 4H-SiC epilayers was studied using high spatial resolution optically detected lifetime measurements. Full wafer mapping with 200μm spatial resolution revealed carrier lifetime variations associated with structural defects replicated from the substrate, and variations in the epitaxial growth conditions due to susceptor design. High-resolution mapping of smaller regions with lateral step sizes down to 20μm revealed local carrier lifetime reductions associated with various defects in the epitaxial layers. Identified defects that influenced carrier lifetime were carrot defects and different types of grown-in stacking fault. Also, clusters of threading screw dislocations in the epilayer probably originating from the dissociation of micropipe in the substrate were found to effectively reduce the carrier lifetime. Furthermore, optically detected lifetime mapping was demonstrated as a non-destructive technique which permitted invisible structural defects to be detected in as-grown epilayers.

Influence of Structural Defects on Carrier Lifetime in 4H-SiC Epitaxial Layers - Optical Lifetime Mapping. J.Hassan, J.P.Bergman: Journal of Applied Physics, 2009, 105[12], 123518