Due to the mosaic growth mode, a high density of threading dislocations was present in epitaxial layers. These bounded misoriented grains. As well as these low-angle (less than 5º) boundaries, high-angle grain boundaries could also be present. An analysis of the Σ = 7 boundary was made here by using circuit mapping to define the Burgers vectors of the dislocations. In certain areas, the boundary was symmetrical with respect to the (21•0) boundary plane. The periodic structure comprised an array of only one type of dislocation, but the cores of these dislocations exhibited more than one atomic configuration.

The Atomic Structure of Threading Dislocations from Low-Angle to High-Angle Grain Boundaries in GaN/Sapphire Epitaxial Layers V.Potin, G.Nouet, P.Ruterana, R.C.Pond: Physica Status Solidi B, 1999, 216[1], 645-8