Triangle-shaped defects are one of the most common surface defects on epitaxial growth of 4H-SiC epilayer on nearly on-axis SiC substrate. In this paper, we investigate the feature and structure of such defects using Nomarski optical microscopy (NOM), micro-Raman spectroscopy and high resolution transmission electron microscopy (HR-TEM). It is found that triangle-shaped defects were composed of a thick 3C-SiC polytype, as well as 4H-SiC epilayer.
A molecular statics method has been used to examine the Ehrlich-Schwoebel (ES) barrier for an adatom of 4H-SiC to diffuse from the {0001} to the {11-20} facet. As the calculated results shown, for the C-terminated surface, the inverse ES barrier exist for the silicon adatom, which could cause the step bunching; for the Si-terminated surface, ES barrier exist for the carbon adatom, which could cause the step meandering and result in the transition of step-flow growth to 2D-nucleation growth. Simultaneously, the C-terminated surface is more stable than the Si-terminated surface, which may be one reason that the quality of film grown on the carbon facet substrate is better.
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