Correlative analysis on InGaN/GaN nanowires: structural and optical properties of self-assembled short-period superlattices

The influence of self-assembled short-period superlattices (SPSLs) on the structural and optical properties of InGaN/ GaN nanowires (NWs) grown by PAMBE on Si (111) was investigated by STEM, EDXS, mu-PL analysis and k center dot p simulations. STEM analysis on single NWs indicates that in most of the studied nanostructures, SPSLs self-assemble during growth. The SPSLs display short-range ordering of In-rich and In-poor InxGa1-xN regions with a period of 2-3 nm that are covered by a GaN shell and that transition to a more homogenous InxGa1-xN core. Polarization- and temperature- resolved PL analysis performed on the same NWs shows that they exhibit a strong parallel polarized red-yellow emission and a pre-dominantly perpendicular polarized blue emission, which are ascribed to different In-rich regions in the nanostructures. The correlation between STEM, mu-PL and k center dot p simulations provides better understanding of the rich optical emission of complex III-N nanostructures and how they are impacted by structural properties, yielding the significant impact of strain on self-assembly and spectral emission.