Effect of a $por$-Si buffer layer on the structure and morphology of epitaxial In$_{x}$Ga$_{1-x}$N/Si(111) heterostructures

Integrated heterostructures exhibiting nanocolumnar morphology of the In$_{x}$Ga$_{1-x}$N/Si(111) 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 structural and microscopic methods of analysis, it is shown that the growth of In$_{x}$Ga$_{1-x}$N nanocolumns on a nanoporous buffer layer offers a number of advantages over growth on $c$-Si. The $por$-Si substrate predetermines the preferential orientation of the growth of In$_{x}$Ga$_{1-x}$N) nanocolumns closer to the Si(111) orientation direction and makes it possible to produce In$_{x}$Ga$_{1-x}$N nanocolumns with a higher degree of crystallographic uniformity and with a nanocolumn lateral size of $\sim$40 nm unified over the entire surface. The growth of In$_{x}$Ga$_{1-x}$N nanocolumns on a $por$-Si layer yields a decrease in the strain components $\varepsilon_ {xx}$ and $\varepsilon_{zz}$ and in the density of edge and screw dislocations compared to the corresponding parameters for In$_{x}$Ga$_{1-x}$N nanocolumns grown on $c$-Si. The In$_{x}$Ga$_{1-x}$N nanocolumnar layer fabricated on $por$-Si exhibits a 20% higher charge-carrier concentration compared to the layer grown on $c$-Si as well as a higher intensity of the photoluminescence quantum yield (+25%).