The morphology of surface features generated by dislocations present at 4H-SiC epitaxial layer surfaces was investigated by fore-scattered electron detection 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 fore-scattered electron detection emanating from sharp-apex pits and verified by Nomarski optical microscopy. A mechanism was proposed to explain the fore-scattered electron detection contrast exhibited by these tail-like features. This mechanism related 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. These results illustrated the various capabilities of fore-scattered electron detection for surface imaging as compared to atomic force microscopy and Nomarski optical microscopy.

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