High optical quality ZnO epilayers grown on sapphire substrates by reactive magnetron sputtering of zinc target

Zinc oxide (ZnO) epilayers were grown on (0 0 0 1) sapphire substrates by reactive sputtering of a zinc target at substrate temperatures of 300 and 600 °C. High-resolution X-ray diffraction, UV–visible and photoluminescence (PL) measurements were carried out to obtain information about epitaxy, micro-structure and optically active defects in these epilayers. Though the epilayer deposited at 600 °C showed a slightly smaller crystallite size along the growth direction as compared to that deposited at 300 °C, it was much superior in terms of other micro-structural parameters. It exhibited significantly small values of micro-strain (2×10−4), rocking curve width (∼0.13°), mosaic twist (0.35°), and screw (6.6×108 cm−2)- and edge (2.9×1011 cm−2)-type dislocation densities. Absorption and PL studies showed the high optical quality of the ZnO epilayer deposited at 600 °C, which exhibited a narrow (full-width at half-maximum—FWHM∼96 meV) and intense band edge luminescence at room temperature. The micro-structural parameters and the sharp PL peak show that the reactively sputtered ZnO epilayer grown at 600 °C is comparable in epitaxial and optical quality with ZnO grown by other epitaxial processes.