During epitaxy of GaN on sapphire grains form a mosaic structure. The distance between edge dislocations in these boundaries was from 2 to 15nm. The strain around the dislocations was quantitatively measured by processing of high-resolution transmission electron microscopic images. The dislocation core distribution maps and in plane Burgers vectors components were derived from the experimental strain tensor by applying the continuum dislocation theory. Experimental results were compared with the atomic models of edge dislocations calculated by using a modified Stillinger-Weber potential for different atomic configurations of the cores. It was concluded that the strain field extracted from simulated images matches with that of observed dislocations. Starting from experimental distortion distribution data, the finite element calculations were used to estimate the stress around the boundaries.

The Dislocations of Low-Angle Grain Boundaries in GaN Epilayers - a HRTEM Quantitative Study and Finite Element Stress State Calculation. S.Kret, P.Dluzewski, G.Maciejewski, V.Potin, J.Chen, P.Ruterana, G.Nouet: Diamond and Related Materials, 2002, 11[3-6], 910-3