ABSTRACT
Cracks are often found in epitaxial layers of AlGaN, grown on GaN buffer layers, which are under tensile stress due to lattice misfit. In the III-nitrides, cracks form triangular networks populating each of the planes with equal probability. The crack is seen to contact the pit exactly at one of its apices and to propagate along a direction parallel to an edge of the pit. It should also be observed that the pit is wider than the crack and must have preceded it. In addition to the pits which are part of a crack a significant background density of free pits exist. Cracks may propagate outwards from the species of the hexagonal pits in all directions. Thus mid crack, end crack, and "V" and "Y" junctions have been found co-located with pits.
