The nanorods were grown in the Semiconductor Epitaxy Group by using the advantages of both a metal-organic vapour-phase epitaxy system and a molecular beam epitaxy reactor on r-plane sapphire substrates. No catalysts or masks were necessary to obtain nanocolumns with outstanding crystalline and optical quality.

Depending on the growth conditions, it was possible to vary the density of the columns over two orders of magnitude. The optical quality and the low impurity-level were proven by microphotoluminescence measurements performed by the Semiconductor Optics Group at the IFP. The exciton-related emission shows linewidths that are unmatched for the growth of gallium nitride nanocolumns. To further confirm the high structural quality of the rods, transmission electron microscopy investigations (Electron Microscopy Group) and synchrotron radiation studies (Semiconductor Surface Group) are on the way.

The next steps are the realization of heterostructures (for example, alternating AlN/GaN layers or InGaN quantum wells) to create LED structures as well as the integration of a single quantum dot into such a nanocolumn to fabricate a single-photon emitter.

The researchers presented their work in Nanotechnology.