Characterization of morphological defects related to micropipes in 4H-SiC thick homoepitaxial layers

A new type of morphological defects related to substrate micropipe is observed in 4H-SiC thick homoepitaxial layers. The structure and formation mechanism are investigated by optical microscopy, laser microscopy, scanning electron microscopy, micro-Raman spectroscopy, micro-photoluminescence spectroscopy and molten KOH etching. The observed new defect has truncated hexagonal prism morphology with a closed-core hexagonal pit, and it is 4H-SiC without polytype transition. It is found that the micropipe in the substrate can not only extend to the epilayer, but also cause a morphological defect to disturb the step-flow growth on the epilayer surface. A model has been proposed to interpret the formation mechanism of the morphological defect. It show that the morphology of the observed defect is mainly determined by the wider terrace in 4 degrees off-angle substrate, the interaction between step-flow growth and spiral growth, and the thickness of the epilayer.