Growth and Optical Characterization of In-Plane-Ordered AlN Nanowires for UV–C Emitting Devices

In recent years, solid-state C-ultraviolet emitters (<230 nm) have become important for disinfection applications. AlN nanowire-based LEDs could be a promising option for this purpose. Here, the growth of AlN nanowires by plasma-assisted molecular beam epitaxy on in-plane ordered GaN pedestals was investigated. The influence of growth temperature and the Al/active N ratio on the morphology of AlN nanowires indicates the role of the Al adatom diffusion length on both the top and sidewalls. In addition, we found that the relative geometrical arrangement of Al effusion cells and N plasma cells with respect to sample normal drastically affects nanowire morphology, opening the path to the controlled formation of GaN/AlN core/shell nanowire heterostructures. Cathodoluminescence experiments revealed a correlation between the near-band edge optical signature and nanowire morphology, with the sharpest band edge emission peaks corresponding to nanowires grown under migration-enhanced epitaxy conditions.