New buffer sublayers for heteroepitaxial III–V nitride films on sapphire substrates

It is suggested to deposit III–V nitride films onto sapphire substrates upon preliminary deposition of a buffer sublayer of a crystalline material with a cubic structure. It is shown experimentally that the deposition of a heteroepitaxial niobium sublayer onto a (0001)-oriented sapphire substrate or a niobium nitride sublayer onto a ( 11 20 )-oriented Al2O3 substrate eliminates a 30° rotation of the (0001)-oriented nitride film in the substrate plane. The elimination of this rotation provides considerable reduction of the lattice mismatch between the substrate and the nitride film, which, in turn, should increase the degree of crystal perfection of the film. In addition, the planes of semiconductor nitride films become parallel to the natural cleavage planes of the substrate. This fact provides for the possibility of manufacturing a heterolaser with a Fabry-Perot resonator, in which the role of the mirrors is played by natural cleavage planes of the film.