A new method was approached to reduce the dislocation density of hydride vapour phase epitaxially grown GaN epilayers. By this method, state of the art quality, GaN layers were grown on sapphire substrates with an in situ treatment of SiNx via the hydride vapour phase epitaxy process. It was found out that the in situ treatment worked most effectively when introduced after the deposition of the nucleation layer. Amorphous SiNx served as a mask allowing only selective growth of GaN seeds as confirmed by scanning electron microscopy analysis and thus a reduction of the dislocation density (down to 106/cm2) with one order of magnitude lower compared to the standard samples (grown without the SiNx treatment) was obtained. Transmission electron microscopy studies revealed that dislocations with a mixed (both screw and edge component) character mostly thread into the GaN layer. Low-temperature photoluminescence showed good optical quality of the layers grown with optimal position of SiNx treatment.

Reduction of the Dislocation Density in HVPE-Grown GaN Epilayers by an in situ SiNx Treatment. H.Ashraf, D.V.Sridhara Rao, D.Gogova, D.Siche, R.Fornari, C.J.Humphreys, P.R.Hageman: Journal of Crystal Growth, 2010, 312[4], 595-600