This work reports on the molecular-beam-epitaxial growth of InGaN/GaN nanowires on Si(111) substrates.The deposition of InGaN in nitrogen-rich conditions on preexisting GaN nanowires allows usto maintain the columnar structure. Wire morphology varies strongly with the indium concentrationin the fluxes. At low nominal In flux, it concentrates in the wire core, resulting in aspontaneous InGaN-GaN core-shell structure. In spite of the high indium content in the core,strain relaxation is purely elastic in these structures. On the other hand, using higher nominal Influxes lead to plastic relaxation and no phase separation is observed. Luminescence is dominatedby carrier localization phenomena, allowing for a low quenching of the emission up to roomtemperature.Studying InGaN insertions con firms that in spite of the small diameter of the wires, growthis dominated by strain relaxation e ffects, and InGaN nucleates as facetted islands. The incorporationof indium occurs preferentially at the top of the islands, resulting in a radial compositiongradient which leads to the spontaneous growth of a core-shell structure.Growth in metal-rich conditions results in a very strong lateral growth, far superior for InGaNthan for GaN : excess In has a surfactant e ffect limiting the axial growth rate and promotinglateral growth.
