<p>The photoluminescence (PL) of Ge/Si nanostructures with Ge quantum dots (QDs) was studied at 5, 78, and 300 K. The nanostructures were grown by molecular beam epitaxy on singlecrystal silicon substrates under 2 keV Ge⁺ ion irradiation and without irradiation. Enhanced intensity of the broad PL band in the energy range of ~0.8 eV was found when the nanostructures were irradiated with Ge⁺ ions. A comparative analysis was carried out for the PL spectra recorded from the side of the silicon substrate and from the side of the formation of Ge/Si nanostructures. During the growth of multilayer Ge/Si nanostructures with Ge QDs at 500–600oC, thermal defects of the structure were found to have formed in silicon, causing the appearance of electron-vibrational bands with zero-phonon lines P ~ 0.767 eV, C ~ 0.789 eV, and H ~ 0.926 eV.</p>