Interplay of phonon and disorder scattering in semiconductor quantum wells

The interplay of radiative relaxation, structural disorder, and phonon scattering on the quantum-well absorption is studied at the level of a fully microscopic theory. Treating light field, phonon, and disorder coupling quantum mechanically, the theory accurately describes the quantum-well absorption for different degrees of disorder at different temperatures. The results show that disorder, phonon, and radiative broadening are not simply additive. The $1s-\mathrm{e}\mathrm{x}\mathrm{c}\mathrm{i}\mathrm{t}\mathrm{o}\mathrm{n}$ resonance deviates from the Lorentzian absorption line shape for narrow linewidths even when only homogeneous broadening is included. Good agreement with experimental absorption measurements on an ${\mathrm{In}}_{0.04}{\mathrm{Ga}}_{0.96}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ quantum-well structure is obtained. It is shown that only a careful evaluation of the comprehensive microscopic model can reliably identify homogeneous and inhomogeneous contributions to the linewidth.