The spatially resolved distribution of strain, misfit and threading dislocations, and crystallographic orientation in non-coalesced GaN layers grown on Si(111) by mask-less cantilever epitaxy or by pendeo-epitaxy on SiC was studied by white beam Laue X-ray microdiffraction, scanning electron and orientation imaging microscopy. Tilt boundaries formed at the column/wing interface depending on the growth conditions. A depth dependent deviatoric strain gradient was found in the GaN. The density of misfit dislocations as well as their arrangement within different dislocation arrays was quantified. Two different kinds of tilt (parallel and perpendicular to the stripe direction) manifested themselves by mutually orthogonal displacements of the (00▪6) GaN Laue spot relative to the Si(444) Laue spot. The origin of the tilts was discussed with respect to the miscut of the Si(111) surface and misfit dislocations formed at the interface. Regular oscillations of the conventional wing tilt were observed. Irregular crystallographic tilts fluctuations were found in the direction parallel to stripes. The amplitude of fluctuations was an order of magnitude smaller for layers with a lower defects density.

Characterization of Growth Defects in Thin GaN Layers with X-Ray Microbeam. R.I.Barabash, G.E.Ice, C.Roder, J.Budai, W.Liu, S.Figge, S.Einfeldt, D.Hommel, R.F.Davis: Physica Status Solidi B, 2007, 244[5], 1735-42