Carrier effects on the excitonic absorption in GaAs quantum-well structures: Phase-space filling

The carrier effects on the excitonic absorption in GaAs quantum-well structures have been investigated both theoretically and experimentally. A two-dimensional model was used to calculate the oscillator strength and binding energy of excitons associated with filled subbands, with phase-space filling being taken into account. The calculation gives explicitly the oscillator strength of excitons as a function of two-dimensional carrier density. The results are compared with measured absorption data from a series of p-type modulation-doped GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As multiple-quantum-well structures, and quantitative agreement is obtained. The calculation shows that the effect of phase-space filling on the binding energy of a bound state can be described by an effective dielectric constant as a function of carrier density. It predicts the decrease of exciton binding energy with carrier density due to phase-space filling, which has been experimentally observed.