Extended defects in GaN films grown at high growth rate

A description of the present knowledge of the layer microstructure typical for thick GaN films grown at high growth rates is presented. The GaN layers are grown by hydride vapour phase epitaxy on sapphire and different buffers are used. The variety of extended defects present in such highly mismatched system are summarized. with the emphasis on their impact on the crystal quality. The defects are reviewed in two main categories according to the microstructural development during growth: large-scale nonuniformities and microstructural crystallographic defects. The first category comprises three-dimensional structural features developed mainly in the interface region, while the second are 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 our understanding of the correlation of growth parameters and microstructure.