The ability of in situ SiNx interlayers to lower the density of threading dislocations was studied for the growth of c-plane (00▪1) GaN epilayers on sapphire by organometallic phase-phase epitaxy. The threading dislocation density in the films may be reduced by up to a factor of 50 to 9 x 107/cm2 and depended upon the SiNx coverage and the conditions of the overgrowth. The threading dislocation reduction method relies on the formation of facetted islands on the SiNx-treated GaN surface and the formation of dislocation half-loops between bent-over threading dislocations during the lateral overgrowth. Dislocations that were not annihilated at the interfacial region during the interlayer overgrowth may bend over at the islands’ inclined side facets and annihilate at their coalescence boundaries. Thus, the threading dislocation density was reduced at the expense of greater film thickness by increasing the SiNx coverage and delaying intentionally the coalescence of the GaN islands.

Threading Dislocation Reduction in (0001) GaN Thin Films using SiNx Interlayers. M.J.Kappers, R.Datta, R.A.Oliver, F.D.G.Rayment, M.E.Vickers, C.J.Humphreys: Journal of Crystal Growth, 2007, 300[1], 70-4