Influence of a por-Si buffer layer on the optical properties of epitaxial In$_{x}$Ga$_{1-x}$N/Si(111) heterostructures with a nanocolumnar film morphology

Integrated heterostructures exhibiting a nanocolumnar morphology of the In$_{x}$Ga$_{1-x}$N film are grown on a single-crystal silicon substrate ($c$-Si(111)) and a substrate with a nanoporous buffer sublayer (por-Si) by molecular-beam epitaxy with the plasma activation of nitrogen. Using a complex of spectroscopic methods of analysis, it is shown that the growth of In$_{x}$Ga$_{1-x}$N nanocolumns on the por-Si buffer layer offer a number of advantages over growth on the $c$-Si substrate. Raman and ultraviolet spectroscopy data support the inference about the growth of a nanocolumn structure and agree with the previously obtained X-ray diffraction (XRD) data indicative of the strained, unrelaxed state of the In$_{x}$Ga$_{1-x}$N layer. The growth of In$_{x}$Ga$_{1-x}$N nanocolumns on the por-Si layer positively influences the optical properties of the heterostructures. At the same half-width of the emission line in the photoluminescence spectrum, the emission intensity for the heterostructure sample grown on the por-Si buffer layer is $\sim$25% higher than the emission intensity for the film grown on the $c$-Si substrate.