Mechanisms of defect formation in ingots of 4H silicon carbide polytype

Abstract

The methods of optical microscopy and X-ray diffractometry have been used to study the features of defect structure in ingots of the SiC-4H polytype; the ingots have featured different diameters and have been grown by the modified Lely method on seeds with deviations of several degrees from the exact orientation (0001)C in the direction 〈11$\bar 2$0〉 (off-cut (0001) seeds). The slip bands observed in the crystals are extended along the [11$\bar 2$0] direction and correspond to the secondary slip system of threading dislocations a/3〈11$\bar 2$0〉{$\bar 1$100} for hexagonal close packing (HCP) crystals. Low-angle dislocation boundaries directed along [1$\bar 1$00] accommodate the disorientation of neighboring domains, which results from their mutual rotation around the [0001] axis. Enlargement of ingots leads to some increase in the dislocation density, mainly due to threading edge dislocations. The average density of micropipes is in the range of 5–20 cm⁻² and practically remains unchanged as the ingot size is increased.