Dislocation conversion in 4H silicon carbide epitaxy

The propagation of basal plane dislocations from off-axis 4H silicon carbide substrates into the homo-epitaxial layers has been investigated using chemical etching, optical microscopy, and transmission electron microscopy (TEM). The etch pit densities of threading edge and basal plane dislocations changed significantly across the epilayer/substrate interface. We have observed conversion of basal plane dislocations in the substrates into threading edge dislocations in the epilayers. TEM observation revealed that the threading dislocations in the epilayers are inclined from the c-axis toward the down-step direction. The conversion is interpreted as a result of the image force in the epilayers between flowing growth steps and basal plane dislocations. This effect can lead to an apparent improvement of the structural quality of epilayers compared to that of substrates. (C) 2002 Elsevier Science B.V. All rights reserved.