Dynamics of exciton relaxation in GaAs/AlxGa1−xAs quantum wells

We present an experimental study of the photoluminescence (PL) rise time of a single GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum well. The PL rise time is investigated as a function of the excitation energy for different temperatures at low excitation densities (≊${10}^{\mathrm{-}8}$ ${\mathrm{cm}}^{\mathrm{-}2}$). A significant slowing down of the relaxation process is observed at low temperature when exciting the quantum well at the light-hole exciton energy; the slowing down disappears as either the temperature or the excitation power is increased.