Heteroepitaxial electrodeposition of zinc oxide films on gallium nitride

Abstract

Epitaxial zinc oxide films have been prepared on gallium nitride (0002) substrates by cathodic electrodeposition in an aqueous solution containing a zinc salt and dissolved oxygen at 85 °C. The films have the hexagonal structure with the c axis parallel to that of GaN and the [100] direction in ZnO parallel to the [100] direction in GaN in the (0002) basal plane. The structural quality is attested by the values of the full width at half maximum in θ/2θ x-ray diffraction (XRD) diagrams [0.07° for the (0002) peak] and in five circles XRD diagrams [0.74° for the ZnO (101̄1) planes compared to 0.47° for the GaN (101̄1) planes]. The morphology of the layers has been studied by scanning electron microscopy. Before coalescence, arrays of epitaxial single crystalline hexagonal columns are observed with a low dispersion in size, indicating instantaneous tridimensional nucleation. Preliminary results on luminescence properties of the films before and after annealing are presented.