Dislocations in 4H-SiC Substrates and Epilayers

Silicon carbide (primarily 4H-SiC) is a wide energy bandgap semiconductor highly suitable for various high-temperature and high-power electronic technologies due to its large energy bandgap, thermal conductivity, and breakdown voltage among other outstanding properties. Large area high-quality single crystal wafers are the chief requirement to realize the potential of silicon carbide for these applications. The lowering of defect densities particularly dislocations in silicon carbide crystals has been an ongoing effort and considerable advances have been made in silicon carbide single crystal growth technology through understanding of growth mechanisms and defect behavior. The primary characterization technique employed is synchrotron X-ray topography, both white beam and monochromatic, which has played a pivotal role in imaging and analyzing defect behavior. Micropipes, threading screw and mixed dislocations, basal plane and threading edge dislocations, and their interactions are discussed along with their behavior during bulk and thin film crystal growth. Dislocation multiplication by the hopping Frank-Read source mechanism, interactions between threading c, a, and c+a dislocations and deflections of threading dislocations resulting in stacking fault formation, relationship between basal plane dislocation distribution and basal plane bending in bulk crystals have been observed and analyzed. Some insights into dislocation behavior during early stages of PVT growth have been obtained from analysis of thin layers of PVT-grown material on seeds. In epilayers, enhanced understanding of the conversion of basal plane dislocations into threading edge dislocations, dislocation susceptibility to recombination enhanced dislocation glide, relaxation of epilayers and the nucleation mechanism of dislocation half-loop arrays, and the effect of surface scratches are described.