Abstract
The spatially resolved distribution of strain, misfit and threading dislocations, and crystallographic orienta-tion in uncoalesced GaN layers grown on Si(111) by maskless 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 is found in the GaN. 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 displacement of the (0006)GaN Laue spot relative to the Si (444) Laue spot. Origin of tilts is 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 direc-tion parallel to stripes. The amplitude of fluctuations is an order of magnitude smaller for layers with a lower defects density.
