A strain-driven GaN interlayer method for reducing dislocation densities in GaN grown onto (111)-oriented silicon by metal organic vapour phase epitaxy was demonstrated. In order to achieve crack-free GaN layers of reasonable thickness and dislocation density, it was essential to integrate both dislocation reduction and strain-management layers. In contrast to techniques such as FACELO or nanoELO, the in situ formation of GaN islands directly on an AlN nucleation layer without the need to deposit a SiO2 or SiNx mask was demonstrated. A graded AlGaN layer for strain management could be grown on top of this dislocation reducing 3D GaN inter-layer in order to achieve crack-free GaN layers grown on top of the AlGaN strain management layer. Furthermore, an additional SiNx layer for subsequent dislocation reduction could also be incorporated into the structure and was shown to reduce efficiently the dislocation density down to the low 109/cm2 level. The structural properties of the 3D GaN island buffer layer and overgrown samples were studied by means of scanning electron microscopy, cross-sectional, and plan-view transmission electron microscopy. Cathodoluminescence in a scanning electron microscope was used to correlate the dislocation microstructure, as observed by plan-view transmission electron microscopy, with luminescent properties.

Dislocation Reduction in GaN Grown on Si(111) Using a Strain-Driven 3D GaN Interlayer. M.Häberlen, D.Zhu, C.McAleese, T.Zhu, M.J.Kappers, C.J.Humphreys: Physica Status Solidi B, 2010, 247[7], 1753–6