EXCITONIC PROPERTIES OF ZNSE/ZNSES SUPERLATTICES

We report an optical investigation of the excitons in ZnSe/ZnSeS superlattices of well widths ranging between 2 and 15 nm. An almost constant exciton binding energy is found. The exciton confinement is found to be dominated by the hole quantization, consistent with the expectation of negligible conduction-band discontinuity in these heterostructures. The effect of strain has been included to properly reproduce the well width dependence of the light-hole energies. Finally strong evidence of hot exciton photogeneration is obtained from the oscillatory behavior of the photoluminescence excitation spectra. This is consistent with the strong exciton-phonon coupling deduced from the temperature dependence of the excitonic linewidth measured by transmission experiments.