Defect formation mechanism of bulk SiC

There are two kinds of defects, planar defects and vertical defects which are called micropipes in SiC bulk crystals grown by the sublimation method. We could decrease these defects by adding a little piece of Si to the SiC powder or using a Ta cylinder in the crucible. We report the dependence of these defects in a wafer on the silicon/carbon ratio. It is important to control the chemical species on the substrate.