Embedded voids formation by overgrowth on GaN nanowires for high-quality GaN films

We report on the epitaxial growth of GaN films on GaN nanowires. GaN nanowires were prepared by the mask-less dry etching technique. The etched, then annealed nanowires form semi-polar and non-polar plane facets with hexagonal symmetry. The different growth rates on the different plane facets result in the formation of void networks. These networks of embedded voids are located near the sapphire substrate, where a high density of dislocations is present. The voids, a few microns in length and a fraction of a micron in diameter, offer free surfaces for dislocation termination, enabling the embedded void approach (EVA) to reduce dislocations. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) studies show uniform reduction of the dislocation density over large area substrates by about three orders of magnitude and lower surface roughness than the GaN starting material.