Heteroepitaxial electrodeposition of zinc oxide films on gallium nitride

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 degrees 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 theta/2 theta x-ray diffraction (XRD) diagrams [0.07 degrees for the (0002) peak] and in five circles XRD diagrams [0.74 degrees for the ZnO (10 (1) over bar 1) planes compared to 0.47 degrees for the GaN (10 (1) over bar 1) 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. (C) 1999 American Institute of Physics. [S0003-6951(99)03348-3].