a b s t r a c tA substantial improvement of the structural quality of GaN/AlN grown on He implanted Si has been described. Many misfit dislocations were redirected from the Al/Si interface and propagated to the Si substrate due to the formation of He bubbles in the substrate. Growth temperature of GaN/AlN was chosen to be the annealing temperature necessary for He bubble formation. The dependence on the He fluence, distance of He bubbles from the Si surface and cleaning procedure of the Si before growth have been described. The structural perfection of the GaN/AlN layers was compared to the layers grown on un-implanted Si.