Dynamics of exciton transfer between the bound and the continuum states in GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As multiple quantum wells

Experimentally observed two-exponential decay of excitonic transitions in GaAs-${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As multiple quantum wells has been successfully interpreted in terms of the exciton transfer between the continuum (free carriers) and the bound states. The calculation results obtained from this exciton-transfer model are in excellent agreement with experimental observations. The rates of the exciton transfer and the free-carrier recombination have been obtained. We have demonstrated that the emission-energy dependence of the decay time constant of the slower decay component is caused by the variation in exciton binding energy induced by interface roughness in the quantum wells.