Growth of epitaxial zinc oxide thin films onto gallium nitride by electrodeposition from a dimethylsulfoxide based electrolytic solution

Abstract

Zinc oxide films have been electrochemically grown on gallium nitride substrates from an electrolytic bath composed of a zinc salt and oxygen dissolved in dimethylsulfoxide (DMSO). The XRD structural study showed the epitaxial growth of the films, specifically it was found that the c axis is perpendicular to the plane of the substrate, while a and b axes are aligned with the respective substrate lattice parameters. In spite the similarity of both crystal structures and the close values of their lattice parameters, for thinner films it was possible to detect acomponent under in-plane compression while thicker films presumably relax. The obtained Poisson's ratio for ZnO was in good agreement with tabulated values, indicating a real effect of elastic deformation and confirming the consistency of the performed analysis. The optical propertiesof the performed electrodeposited film showed that the transmittance spectra have a very similar general shape in comparison with the one of the substrate but with an increase in the totaloptical transmittance. Due to presence of ZnO, the diffused reflectance spectra showed also an increased absorption close to 400 nm. As a consequence of the difference in the defect density,the photoluminescence measurements recorded in stressed and relaxed samples also changes drastically. © 2013 by ESG.