Threading dislocations could be reduced by in situ deposition of intermediate SiNx sub-monolayers in group III-nitride heterostructures and their ternary alloys. Here efficient dislocation density decreasing at the SiNx nano-mask was observed in an AlxGa1-xN layer with x = 0.2 grown epitaxially onto c-plane sapphire by low-pressure MOVPE. However high annihilation efficiency was not achieved homogenously along the whole SiNx interface in the samples. Areas with high and low annihilation grade alternated along the interface in accordance with respective variations in the SiNx distribution. Furthermore an unusual dislocation bundling was observed for the dislocations in areas with high dislocation densities above the SiNx interface, leading to large areas of several μm2 with low dislocation densities at the surface between the dislocation bundles. By using growth interrupted samples under same growth conditions, it was possible to investigate the heterostructures in different growth stages by cross-sectional TEM. This permitted the correlation of dislocation propagation with growth-mode variations in AlGaN deposited on the SiNx interlayer and the development of a growth model for AlGaN layer grown on the SiNx nano-mask.

TEM Investigations on Growth Interrupted Samples for the Correlation of the Dislocation Propagation and Growth Mode Variations in AlGaN Deposited on SiNx Interlayers. O.Klein, J.Biskupek, K.Forghani, F.Scholz, U.Kaiser: Journal of Crystal Growth, 2011, 324[1], 63-72