InGaN nanostructures are among the most promising candidates for visible solid-state lighting and renewable energy sources. To date, there is still a lack of information about the influence of the growth conditions on the physical properties of these nanostructures. Here, we extend the study of InGaN nanowires growth directly on Si substrates by plasma-assisted molecular beam epitaxy. The results of the study showed that under appropriate growth conditions a change in the growth temperature of just 10 °C leads to a significant change in the structural and optical properties of the nanowires. InGaN nanowires with the areas containing 4%–10% of In with increasing tendency towards the top are formed at the growth temperature of 665 °C, while at the growth temperatures range of 655 °C–660 °C the spontaneously core–shell NWs are typically presented. In the latter case, the In contents in the core and the shell are about an order of magnitude different (e.g. 35% and 4% for 655 °C, respectively). The photoluminescence study of the NWs demonstrates a shift in the spectra from blue to orange in accordance with an increase of In content. Based on these results, a novel approach to the monolithic growth of In x Ga1−x N NWs with multi-colour light emission on Si substrates by setting a temperature gradient over the substrate surface is proposed.

In this work, it is experimentally shown that the etching of GaN or InGaN NWs in the KOH solution allows managing the morphology and optical properties of the nanowires array. Thinning rate of GaN nanowires is 5 times slower than the rate for InGaN nanowires along semi-polar and non-polar direction for nanowires with Ga-polar crystal structure. The diameter of the InGaN NWs decreases from 200-100 to 30-40 nm. After etching process, the intensity photoluminescence (PL) of nanowires and uniformity PL signal at all sample area increase.

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The possibility of the controlled removal of GaN nanowires (NWs) from an SiOx inhibitor layer of patterned SiOx/Si substrates has been demonstrated. It has been found that the wet KOH etching preserves the selectively grown GaN NWs on Si surface, whereas the GaN NWs grown on inhibitor SiOx layer are removing. The effect is described by the difference in polarity between GaN NWs grown on a Si surface and NWs grown on a SiOx inhibitor layer.