PROPERTIES OF ZN1-XCDXS TERNARY AND ZN1-XCDXS1-YSEY QUATERNARY THIN-FILMS ON GAAS GROWN BY OMVPE

OMVPE growth and properties of Zn(1-x)Cd(x)S ternary and Zn(1-x)Cd(x)S(1-y)Se(y) quaternary epilayers lattice-matched to GaAs are described. These materials are expected to posses promising characteristics for optoelectronic applications in the blue to the near-ultraviolet spectral region. First, we investigated the growth conditions for lattice-matching and achieved single-crystalline cubic materials. For ternary epilayers, the bowing parameter for bandgaps was slightly larger than that for the hexagonal material (0.3 eV), and the closely lattice-matched epilayer showed a bandgap of 2.77 eV (448 nm). The strong photoluminescence peak at 4.2 K was considered to be excitonic emission. For quaternary epilayers, we obtained the growth conditions for obtaining closely lattice-matched epilayers with a bandgap of 2.6 eV (477 nm), which is a purer blue compared to the lattice-matched ternary epilayer, but the photoluminescence was dominated by structural defects.