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Interband optical transitions in GaAs modulation-doped quantum wells: photoreflectance experiment and self-consistent calculations

Photoreflectance spectra of AlGaAs/GaAs/AlGaAs wide quantum wells doped by Si up to Nd = 2 x 1018cm-3 were investigated at room temperature. Three kinds of spectral peculiarities were observed in photoreflectance spectra: a spectral line due to the GaAs band gap (1.42 eV), short-period Frantz–Keldysh oscillations originating from the barrier band gap (1.71 eV) and lines of subbands in the quantum well. The energies of optical transitions are determined by means of the least-squares approximation of experimental data by the sum of Aspnes relations. The experimental results are in good agreement with the self-consistent subband structure calculation. It is shown that with an increase of the doping level the energies of the interband transitions in the quantum well are changed.