Long radiative lifetimes of biexcitons in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells

The dynamics of biexciton radiative decay in semiconductor quantum wells is treated within the excitonic-molecule mode including super-radiance, exciton recoil, and nonzero photon momentum. For parameters describing GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells, we find that the rate for the decay of the excitonic molecule (in the ground state of the relative motion between excitons) into an exciton and a photon is less than the decay rate characteristic of radiative free one-excitons.