Effect of Image Charge on Exciton Binding Energy in ZnS/Be_xZn_1-xS Quantum Wells

Abstract

We calculate the binding energies of heavy-and light-hole excitons in ZnS/Be x Zn 1Àx S single quantum wells (SQWs) as functions of well width using a variational method by considering the effect of the mismatch between the dielectric constants of the well and barriers (effect of image charge). The increases in the heavy-and light-hole exciton binding energies in ZnS/Be x Zn 1Àx S SQWs at a Be content (x ) equal to 0.76 are estimated to be 29.9 and 28.2 meV, respectively. For narrow wells, the heavy-and light-hole exciton binding energies calculated by considering the effect of image charge exceed the longitudinal optical phonon energy of ZnS for x ! 0:2.