Determination of the diffusion length of nonequilibrium carriers in CdS/ZnSe/ZnSSe heterostructures designed for semiconductor disk lasers

Cathodoluminescence of a heterostructure with CdS/ZnSe/ZnSSe quantum wells at different electron energies in the range of 3–7 keV has been studied. The dependence of the ratio of the radiation intensity of the quantum well to the intensity of radiation of the ZnSSe barrier layers matched to the GaAs substrate is obtained. This relationship is modeled for different diffusion lengths of nonequilibrium charge carriers in barrier layers and coefficients of trapping of these carriers by a quantum well. It is shown that taking the surface recombination into account gives the best modeling results. An estimate of the diffusion length of nonequilibrium carriers in barrier layers of 25 nm was obtained from comparing the simulation results and the experimental data. The effect of the diffusion length on the characteristics of a semiconductor disk laser based on heterostructures with similar quantum wells is discussed.