Temperature-dependent excitonic absorption in long-period multiple InxGa1−xAs/GaAs quantum well structures

Temperature variations in the fundamental absorption edge of long-period InxGa1−xAs/GaAs structures are studied for samples with different numbers of quantum wells and similar periods. The quantum wells were close in composition and width. Experimental data are interpreted in the model of exciton-polariton light transfer involving localized excitons in confined structures with a finite number of quantum wells. The experimentally observed low-temperature anomaly of the integrated absorption coefficient is attributed to reemission of resonance localized excitons along a finite chain of quantum wells, with no excitonic transfer. The radiative decay time of an exciton in a single quantum well is estimated from the experimental data. It is demonstrated that, at low temperatures, the major contribution to the width of the experimentally observed absorption line corresponding to the ground heavy-hole exciton state is made by inhomogeneous broadening of the line by the field of potential fluctuations associated with the compositional disorder of the alloy. At low temperatures, the inhomogeneous broadening is much more pronounced than the broadening governed by the true radiative and nonradiative dissipative decay.