Growth of ZnO∕MgZnO quantum wells on sapphire substrates and observation of the two-dimensional confinement effect

Abstract

Zn O ∕ Mg Zn O single quantum wells (QWs) in which the well width changes continuously were grown on sapphire (112¯0) substrates by metalorganic chemical vapor deposition. Photoluminescence (PL) measurement revealed two emission peaks: one is position dependent and the other is not. Polarized PL spectra obtained from cleaved facets demonstrated perfect two-dimensional features of the position-dependent emission peak. The position-dependent peak was attributed to emissions due to excitons confined in the ZnO well layer, and the position-independent peak was attributed to emissions due to excitons in MgZnO barrier layers. The width dependence of the emission energy from the ZnO QW was interpreted by a simple theoretical model. Typical PL decay time of the QW emission was 360ps at 77K. It was shorter than that of the MgZnO barrier, 470ps, due to the enhanced confinement effect in the QW.