Structure of “Star” Defect in 4H-SiC Substrates and Epilayers

Abstract

The structure of the “star” defect in 4H-SiC substrates and its effects on the extended defect structures in the epilayers were studied by molten KOH etching and transmission x-ray topography. Star defects consist of a center region with high densities of threading dislocations (both edge and screw types) and six arms of dislocation arrays extending along <11-20> directions. In addition, multiple linear dislocation arrays extending perpendicular to the off-cut direction were observed in the epilayers. Dislocation arrays extending along <11-20> directions are consistent with the slip bands generated by the prismatic slip: a/3<11-20>{1-100}. Bands of linear dislocation arrays extending perpendicular to the off-cut direction correspond to the threading edge dislocations nucleated during epitaxial growth.