A description of the present knowledge of the layer microstructure typical for thick GaN films grown at high growth rates was presented. The GaN layers were grown by hydride vapour phase epitaxy on sapphire and different buffers were used. The variety of extended defects present in such highly mismatched system were summarized, with the emphasis on their impact on the crystal quality. The defects were reviewed in two main categories according to the microstructural development during growth: large-scale non-uniformities and microstructural crystallographic defects. The first category comprises three-dimensional structural features developed mainly in the interface region, while the second were typical extended defects, i.e., dislocations with different Burgers vectors, nanopipes, inversion domain boundaries and stacking faults. The quality of the layers was improved vastly as a consequence of an understanding of the correlation of growth parameters and microstructure.

Extended Defects in GaN Films Grown at High Growth Rate. E.Valcheva, T.Paskova, B.Monemar: Journal of Physics - Condensed Matter, 2002, 14[48], 13269-75