Exciton-binding-energy maximum in ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$As/GaAs quantum wells

The theoretically predicted peaked nature of the exciton binding energy as a function of quantum-well width has been experimentally observed. The values are obtained directly from interband magneto-optical measurements and compared with calculations based on the envelope-function method. The high quality of the samples is demonstrated by the fact that transitions involving Landau quantum numbers up to eight are seen in all wells and are identifiable at magnetic fields below 1 T. This unusually low scattering rate has allowed the binding energies to be obtained at a high degree of accuracy.