Interface excitons in staggered-line-up quantum wells: The AlAs/GaAs case

For spatially indirect excitons in staggered-line-up single quantum wells, binding energies, Bohr radii, and oscillator strengths are calculated, taking into account finite barrier heights and image-charge effects. Numerical results are presented for a model case of particular fundamental importance. For AlAs/GaAs quantum wells, which are indirect in k space, we find binding energies up to 11 meV for the ${\mathit{X}}_{\mathit{z}}$ exciton and 5 meV for the ${\mathit{X}}_{\mathit{x}\mathit{y}}$ exciton. However, no-phonon oscillator strengths fall below the direct exciton by five orders of magnitude. A comparison to experiment suggests that the ${\mathit{X}}_{\mathit{x}\mathit{y}}$ exciton is lowest in energy.