Dislocation Reduction in AlN and GaN Bulk Crystals Grown by HVPE

Abstract

We analyse the dislocation distribution in GaN and AlN bulk crystals by transmission electron microscopy and X-ray diffraction. The crystals are grown by hydride vapour phase epitaxy onto 6H-SiC[0001] and Si(111) substrates. Two essentially different dislocation populations are observed: (i) a-type dislocations that show efficient dislocation density reduction (down to 4 × 105 cm–2) and (ii) a, (a + c) and c-type dislocations each type in a considerable density with less efficient dislocation reduction. We evaluate the dislocation processes that result in this different behaviour as dependent on the dislocation population.