Excitonic absorption in modulation-doped GaAs/AlxGa

摘要: We have performed transmission measurements in a range of undoped through heavily-modulation-doped GaAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As multiple-quantum-well structures. The observed absorption spectra demonstrate quenching the excitonic oscillations with increasing quasi-two-dimensional electron gas. density corresponding to total bleaching lowest oscillation is greater than or equal 3\ifmmode\times\else\texttimes\fi{}${10}^{11}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ for quantum well size 200 A\r{}. Theoretical calculations which include effect carrier screening been made. results show that both long-range and short-range many-body effects should be included explain experimentally spectra. In modulation-doped case, we conclude phase-space filling exchange gas are dominant on absorption. From observation linewidth increases density, exciton lifetime reduces due interaction between electrons excitons.