Droplet epitaxy mediated growth of GaN nanostructures on Si (111) via plasma-assisted molecular beam epitaxy

In this report, we demonstrate that the use of a GaN seeding layer prepared by droplet epitaxy prior to the growth of epitaxial GaN on Si (111) can lead to the formation of oriented arrays of Y-shaped nanoislands (nanotripods) and nanowires and affects the surface density of the nanostructures. From the transmission electron microscopy studies, it is shown that at least some of the seeding islands have a cubic zinc-blende (ZB) GaN structure, and their {111} facets act as the nucleation centers for further growth of GaN nanorods with a wurtzite (WZ) structure. It is also demonstrated that even if the Ga droplets are deposited on the silicon surface prior to the nitridation, a silicon nitride interlayer between silicon and GaN will be inevitably formed in the further growth process. The density and the position of the seeding centers can be controlled with growth parameter variation during the droplet epitaxy; thus the technique proposed and studied in this report can be used for the preparation of site- and density-controlled arrays of nanostructures.