High-resolution observation of basal-plane C-core edge dislocations in 4H-SiC crystal by transmission electron microscopy

High-resolution transmission electron microscopy was used to analyze basal-plane dislocations, which display very characteristic contrasts in grazing incidence monochromatic X-ray topographic images, on the Si-face of 4H-SiC. Grazing incidence monochromatic synchrotron X-ray topography, which is a lattice defect observational technique, has been used in power devices made from 4H-SiC. This technique is useful in analyzing lattice defects near the surface but without the contrast of high-density lattice defects inside the wafer. Basal-plane dislocations exhibit several distinct types of contrast: dark, bright, asymmetric dark/bright and intermediate contrast. Dark and bright contrast areas have been reported to be the edge dislocation regions of basal-plane dislocations. Nevertheless, it remains unclear whether the dark contrast regions are edge dislocations with extra half-planes on the surface side, i.e. Si-core edge dislocations, or those with extra half planes on the deeper crystal side, namely C-core edge dislocations on the Si-face. In this paper, basal-plane dislocations with dark contrast edge dislocations in grazing incidence X-ray topographic images around the (0001) surface were observed via high-resolution transmission electron microscopy, and it was determined that the extra half planes are located on the deeper side against the Si-face. This indicates that the dark contrast edge dislocations are those with a C-core structure on the Si-face. This conclusion is important in establishing the analytical procedure for dislocation contrast in grazing incidence monochromatic X-ray topography on Si face images.