Imaging Surface Pits and Dislocations in 4H-SiC by Forescattered Electron Detection and Photoluminescence
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Forescattered electron detection (FED) was utilized to image surface depressions resulting from threading screw and edge dislocations in 4H-SiC epitaxial layers. These surface depressions, or growth pits, exhibited two morphology types. Screw and edge dislocations could be imaged by photoluminescence and differentiated by their interactions with propagating partial dislocations (PDs). Correlations between FED and photoluminescence showed that sharp-apex pits 1 μm in size and strip-shaped pits 500 nm in size could be linked to individual screw and edge dislocations, respectively. Forescattered electron detection demonstrated sufficient sensitivity to image surface features previously resolvable only by atomic force microscopy. This new technique is nondestructive, noncontact, and capable of rapid, spatial mapping of growth pits resulting from threading screw and edge dislocations in SiC epitaxial layers.