The data on growth peculiarities and physical properties of GaAs insertions embedded in AlGaAs nanowires grown on different (1 1 1) substrates by Au-assisted molecular beam epitaxy are presented. The influence of nanowires growth conditions on structural and optical properties is studied in detail. It is shown that by varying the growth parameters it is possible to form structures like quantum dots that emit in a wide wavelengths range. These quantum dots show sharp and intense emission lines when an optical signal is collected from a single nanowire. The technology proposed opens new possibilities for integration of direct-band A ^III B ^V materials on silicon platform.