The morphology of surface features generated by dislocations present at 4H-SiC epitaxial layer surfaces was investigated by fore-scattered electron detection (FED) inside a conventional scanning electron microscope. Various growth pit morphologies were correlated to dislocation types using molten KOH etching. Specifically, sharp-apex pits and stripe-shaped pits were consistently linked to screw and edge dislocations, respectively. The size and depth of these growth pits were measured by atomic force microscopy. Tail-like features were observed by FED emanating from sharp-apex pits and verified by Nomarski optical microscopy (NOM). A mechanism was proposed to explain the FED contrast exhibited by these tail-like features. This mechanism relates the nature of step-flow and spiral growth in the wake of a screw dislocation to the surface distortions resulting in such tail-like features. The Burgers vector direction could thus be determined based on a purely morphological analysis of these tail-like features. The results of this study illustrate the various capabilities of FED for surface imaging as compared to atomic force microscopy and NOM. The potential for utilizing FED to map dislocation-associated growth pits was discussed.

Nondestructive Dislocation Delineation using Topographically Enhanced Imaging of Surface Morphologies in 4H-SiC Epitaxial Layers. Y.N.Picard, K.X.Liu, R.E.Stahlbush, M.E.Twigg, X.Zhang, M.Skowronski: Journal of Applied Physics, 2008, 103[7], 074904