Band gap engineering based on MgxZn1-xO and CdyZn1-yO ternary alloy films

We describe the structural and optical properties of II-VI oxide alloys, MgxZn1-xO and CdyZn1-yO, grown by pulsed-laser deposition. Single-phase alloyed films of (Mg,Zn)O and (Cd,Zn)O with c-axis orientations were epitaxially grown on sapphire (0001) substrates. The maximum magnesium and cadmium concentrations (x = 0.33 and y = 0.07, respectively) were significantly larger than the thermodynamic solubility limits. The band gap energies systematically changed from 3.0 (y = 0.07) to 4.0 eV (x = 0.33) at room temperature. The photoluminescence peak energy deduced at 4.2 K could be tuned from 3.19 to 3.87 eV by using Cd0.07Zn0.93O and Mg0.33Zn0.67O at both ends, respectively. The lattice constants of the a axis were monotonically increasing functions of the concentrations of both alloys. The exciton-phonon coupling strength was determined in Cd0.01Zn0.99O grown on a lattice-matched ScAlMgO4 substrate. (C) 2001 American Institute of Physics.