Epitaxial lateral overgrowth was used to reduce threading dislocation  densities in GaN. Transmission and scanning electron microscopy studies were made of threading dislocations in GaN films grown by epitaxial lateral overgrowth onto GaN nano-columns produced either during growth by molecular beam epitaxy (method 1), or by self-organised patterning on a uniform layer grown by metal organic chemical vapour deposition (method 2). In method 1, isolated nanocolumns grew without threading dislocations, but some threading dislocations formed when nanocolumns coalesced. Although some of these threading dislocations extended through the overlayer, extensive lateral migration of others, depending on the dislocation type, led to dislocation annihilation, lowering the overall threading dislocation density. In method 2, a similar process of lateral migration of threading dislocations was observed during epitaxial lateral overgrowth, resulting in a continuous GaN overlayer with threading dislocation densities less than 108/cm2.

The Reduction of Threading Dislocations in GaN using a GaN Nanocolumn Interlayer. L.Meshi, D.Cherns, I.Griffiths, S.Khongphetsak, A.Gott, C.Liu, S.Denchitcharoen, P.Shields, W.Wang, R.Campion, S.Novikov, T.Foxon: Physica Status Solidi C, 2008, 5[6], 1645-7