Abstract
A well defined sharp peak was observed in the absorption and luminescence spectra near the absorption edge of n-type modulation-doped GaAs-AlxGa1-xAs multiple quantum wells. The peak is assigned as the Fermi edge anomaly similar to the many-body effects in the soft X-ray spectra of metals. As the temperature was raised above 10 K, the peak disappeared, but it was restored by the application of magnetic field. The magnetic field dependence of the peak indicates that it has an excitonic character.