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

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 (2) over bar0 > (off-cut (0001) seeds). The slip bands observed in the crystals are extended along the [11 (2) over bar0] direction and correspond to the secondary slip system of threading dislocations a/3 < 11 (2) over bar0 >{(1) over bar 100} for hexagonal close packing (HCP) crystals. Low-angle dislocation boundaries directed along [1 (1) over bar 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.