Zinc blende GaAs films grown on wurtzite GaN∕sapphire templates

1-μm-thick zinc-blende GaAs (111) films were grown by molecular-beam epitaxy on wurtzite GaN∕sapphire (0001) templates. In spite of a ∼20% lattice mismatch, epitaxial growth was realized, so that the GaAs films showed good adhesion and their surface had a larger mirror-like area with an average surface roughness of 10 nm. Transmission electron microscopy revealed a flat and abrupt epitaxial GaAs∕GaN interface with some nanocavities and a large number of dislocations. Reasonably good crystalline quality of the GaAs films was confirmed by Raman characterization. Spectroscopic ellipsometry showed sharp interference fringes and characteristic parameters in the range of 0.75–5.3 eV. Photoluminescence study revealed extended band tails and dominance of non-radiative carrier recombination.