Structure and optical properties of ZnO/Mg0.2Zn0.8O superlattices

ZnO/Mg0.2Zn0.8O superlattices with a band-gap offset of about 0.5 eV were e pitaxially grown by laser molecular-beam epitaxy on a sapphire(0001) substr ate using a ZnO buffer layer. The superlattice structure with a period rang ing from 8 to 18 nm was clearly verified by cross-sectional transmission el ectron microscopy, Auger depth profile, and x-ray diffraction. As the well layer thickness decreased below 5 nm, the photoluminescence peak and absorp tion edge in the photoluminescence excitation spectra showed a blueshift, i ndicating a quantum-size effect. (C) 1999 American Institute of Physics. [S 0003-6951(99)04033-4].