The impact of pregrowth conditions and substrate polytype on SiC epitaxial layer morphology

4H and 6H-SiC epitaxial layers exhibit characteristic morphological defects caused by process and substrate interferences with the a-axis directed step-flow growth. 4H-SiC is shown to typically exhibit worse morphology than 6H-SiC for a given off-axis orientation. SiC epitaxial layer defects are significantly reduced by the optimization of growth conditions and substrate surface preparation. The remaining highly variable defects are shown to emanate from the substrate surface with densities of greater than or equal to 1000 cm(-2).