Characterizations of ZnO and Zn sub((1-x))Cd sub(x)O thin films grown on Zn- and O-face ZnO substrates by metal organic chemical vapor deposition

Zn sub((1-x))Cd sub(x)O solid solutions have been grown by us on Zn- and O-polar surfaces of ZnO substrate by metal organic chemical vapor deposition (MOCVD), with the same cadmium flow. We carried out photoluminescence spectroscopy (PL) and optical transmission measurements to investigate the incorporation of cadmium in the layers, as well as its influence on the optical properties. The lattice parameters and the morphology of these films were examined using high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). In our case, the Cd incorporation is obtained at 2.5% for Zn sub((1-x))Cd sub(x)O grown on the Zn-polar surface of ZnO substrate, which is confirmed by the greatest energy shift (237 meV) toward lower energies of the PL emission, and by the appearance of a new peak located at 270 cm super(1) in the Raman spectra. HRXRD studies show that all layers exhibit a wurtzite phase with c-axis orientation. In particular, regarding the Zn sub(0.975)Cd sub(0.025)O layer grown on Zn-face, the in-plane lattice parameter remains unchanged while the c-axis parameter is elongated to 5.399 A.