A process for fabricating a growth substrate comprises preparing a donor substrate by forming a crystalline semiconductor surface layer on a seed layer of a carrier. This preparation comprises forming the surface layer as a plurality of alternations of an InGaN primary layer and of an AlGaN secondary layer, the indium concentration and the thickness of the primary layers and the aluminum concentration and the thickness of the secondary layers being selected so that a homogeneous AlInGaN layer that is equivalent, in terms of concentration of aluminum and indium, to the surface layer has a natural lattice parameter different from the lattice parameter of the seed layer.