Thick high quality GaN layers presenting a dislocation density reduced to 6 x 106/cm2 were grown by hydride vapor phase epitaxy. Scanning electron microscopy characterizations, X-ray double diffraction measurements, photoluminescence and reflectivity experiments, both at 4.5K were carried out to reveal the optical and the structural properties of the GaN epilayers. The strain relaxation was studied as a function of increasing the thickness. Special emphasis was placed to the control of the parasitic nucleation on the reactor wall upstream the substrate, which consistently appears for long-time growth experiments. The amount of the parasitic deposit was quantitatively assessed by theoretical modelling. Attention was paid to accurate characterizations of 450μm thick GaN layers obtained via thickening through a re-growth step after growth interruption and strain relaxation on cooling the templates.

Low Dislocation Density High-Quality Thick Hydride Vapour Phase Epitaxy (HVPE) GaN Layers. Y.Andre, A.Trassoudaine, J.Tourret, R.Cadoret, E.Gil, D.Castelluci, O.Aoude, P.Disseix: Journal of Crystal Growth, 2007, 306[1], 86-93