Dependence of Exciton Linewidth on the Composition of Zn$\text{}_{x}$Mg$\text{}_{1-x}$Se Layers Grown by MBE

This work deals with the study of the photoluminescence and reflectivity properties of Zn$\text{}_{x}$Mg$\text{}_{1-x}$Se epilayers grown by molecular beam epitaxy on (001)GaAs and (111)ZnTe substrates. The photoluminescence spectra of Zn$\text{}_{x}$Mg$\text{}_{1-x}$Se layers grown on GaAs and ZnTe substrates are dominated by blue emission bands. The energetical positions and relative intensities of the bands depend on Mg contents in the epilayers. The shift of the maxima of blue emission toward higher photon energies and a simultaneous steep increase in the linewidth with an increase in Mg concentration are observed. A small amount of Mg added to ZnSe leads to a sharp increase in the linewidth from 2 meV in pure ZnSe layer grown on GaAs substrate to about 180 meV in Zn$\text{}_{0.78}$Μg$\text{}_{0.22}$Se.