Cross-sectional structure of carrot defects in 4H–SiC epilayers

Abstract

Surface morphology of carrot defects in 4H–SiC epilayers is described based on optical microscopy and molten potassium hydroxide etching. Its crystallographic structure is investigated using cross-sectional transmission x-ray topography. A threading screw dislocation in substrate serves as the nucleation source of a carrot. At the beginning of the epitaxial growth, the source dislocation is deflected toward the step-flow direction where a basal plane dislocation and a vertical planar defect nucleate together. The vertical planar defect fills the space between the basal plane dislocation and the deflected threading dislocation. This structure forms characteristic morphology on the epilayer surface, such as groove, shallow trench, etch line of the groove, and hexagonal and oval etch pits at each end of the groove.