Formation of High-Quality GaN Microcrystals by Pendeoepitaxial Overgrowth of GaN Nanowires on Si(111) by Molecular Beam Epitaxy

Hexagonal GaN microcrystals of a size between 1 to 3 mu m are obtained by the pendeoepitaxial overgrowth of a GaN nanowire template on Si(111). The GaN microcrystals are free of threading dislocations and exhibit an atomically smooth surface (roughness of 0.2 nm). Photoluminescence spectra of these microcrystals are dominated by an intense donor-bound exciton transition at 3.471 eV with a width of 1 meV reflecting strain-free GaN of exceptional structural quality.