Distortion of excitonic emission bands due to self-absorption in ZnSe epilayers

In this letter we investigate the influence of self-absorption on the excitonic emission spectra of ZnSe epitaxial layers grown by molecular beam epitaxy on GaAs substrates. We observe that, very often, samples grown under identical conditions show a widely ranging ratio of neutral donor-bound-exciton to free-exciton intensities in photoluminescence (PL). We present experimental evidence to show that these differences can arise from the variations in the epilayer thickness and detailed PL experimental conditions and do not necessarily represent the layer-to-layer purity fluctuations, as the spectral line shapes may suggest.