Exciton line broadening by compositional disorder in alloy quantum wells

Spectral lines of photoluminescence in ${\mathrm{ZnSe}}_{\mathit{x}}$ ${\mathrm{Te}}_{1\mathrm{-}\mathit{x}}$/ZnTe single quantum wells (QW)’s are studied experimentally and theoretically. Special attention is given to the linewidth as a measure of the QW quality. The analysis of band offsets shows that the structures under study are type-II QW’s, where electron levels are quantized inside a QW, whereas holes are situated in the barriers. The spectral linewidth depends rather slightly on the thickness of QW’s, ruling out fluctuations of QW thickness as the dominant broadening mechanism. On the other hand, the theory of line broadening by compositional disorder fits the experimental data well without any adjustable parameters, suggesting that it is the compositional disorder that dominates the line broadening in these systems.