In this work, we study the influence of the substrate temperature on the structural and optical properties of InGaN nanostructures synthesized by plasma-assisted molecular beam epitaxy. We show that ternary InGaN alloys with a chemical composition within the miscibility gap can be synthesized under N-rich growth conditions at the substrate temperatures from 600 to 670 °C. The results can be used to create visible and white light-emitting diodes on Si substrates.