Decomposition Resilience of GaN Nanowires, Crested and Surficially Passivated by AlN

The rapidly increasing interest in nanowires (NWs) of GaN and associated III-Nitrides for (opto-)electronic applications demands immediate address of the technological challenges associated with NW-based device processing. Toward this end, we demonstrate in this work an approach to suppress the thermal decomposition of GaN NWs, which also serves to passivate the surface states. Both of these effects are known to be significant challenges in the development of GaN-NW-based devices. The approach entails AlN capping of the as-grown GaN NWs, in the same molecular beam epitaxy growth step. We show that the epitaxial AlN crest that grows on the top facet of the NW arrests thermal decomposition, while the AlN shell on the sidewalls (together with the crest) protects the NW surface from the generation of oxygen-induced surface states. This simple approach can be used for the development of GaN-NW-based devices.