Formation mechanism of Type 2 micropipe defects in 4H–SiC crystals

Abstract

We report experimental studies on the formation of Type 2 micropipe defects in 4H–SiC crystals grown by a physical vapor transport method. Compared with Type 1 micropipes, Type 2 micropipes exhibit new features allowing them to lie at an oblique angle about 12° to the [0001] crystal axis and are smaller in size than Type 1 micropipes. By changing the growth conditions, we find that a smaller axial temperature gradient and a larger grain size in the SiC source are beneficial to eliminate the Type 2 micropipes. We think that the liquid silicon is responsible for the formation of Type 2 micropipes. A possible formation mechanism for Type 2 micropipes is put forward.