The spatial distribution of defects and its dependence on seed polarity and off-orientation during growth of 4H-SiC single crystals

The defect distribution in 4H-SiC single crystals in dependence on the seed polarity and its off-orientation was investigated by KOH-etching, optical microscopy and X-ray topography. Micropipe density, stacking fault density and dislocation density were determined for 2" crystals grown in < 000-1 > direction 0-7 degrees off towards < 11-20 > and for crystals up to 1" in diameter grown in < 11-20 > or a- and < 1-100 > or m-directions and using repeated a-face growth. For the growth in polar directions the micropipe density and dislocation density decrease with increasing off-orientation of the seed. A similar behavior was found for the stacking fault density and dislocation density in non-polar directions with off-orientation to c-direction. Nevertheless, while the dislocation density could be reduced up to three orders of magnitude for the growth along non-polar directions, the stacking fault density was continuously increasing. Additionally, the defect distribution after repeated a-face growth will be discussed in terms of growth related and kinetic models.