Edge Luminescence of ZnO Films

Abstract

The luminescence spectra of some zinc oxide films near the exciton band have a very wide long-wavelength band. Its intensity increases with the excitation level much more rapidly than the intensity of the exciton bands, which even decreases for some films. It is shown experimentally that the long-wavelength band is not the P-line and is most likely caused by an intrinsic defect or random impurity in the ZnO. An interpretation of this effect based on the Burstein–Moss effect is proposed. A system of rate equations that include a number of parameters is set up for approximate modelling of this effect. These parameters can be chosen so that a numerical solution of this system yields a dependence of the intensity ratio of these bands on the excitation level and (in some cases) a drop in the intensity of the exciton band with increasing excitation level that is close to experiment.