Structural properties of aluminum nitride bulk single crystals grown by PVT

Defect analysis is performed on 1-inch diameter bulk AlN crystals grown on AlN-on-SiC templates by physical vapour transport. The mean density of threading dislocations as evaluated, by wet chemical etching is about 4 x 10(-4) cm(-2); mosaicity of the crystals is mostly inherited from the quality of the SiC and the AlN-on-SiC template used as seed. Comparing crystals grown without, and with growth optimization, the dislocation topography, is significantly different, and in crystals grown under optimized conditions, low angle grain boundaries have a more pronounced tendency to dissolve into dislocation bunches and thus a lower density at the crystal top. This corresponds to a 'coarser' mosaic structure as observed in X-ray rocking curve measurements, In summary, AlN bulk crystals grown on AlN-on-SiC templates under optimized conditions show not only significant improvement in tracking mitigation and optical homogeneity, but also in structural quality, within a single growth run.