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Photoluminescence study of V-groove quantum wires: The influence of disorder on the optical spectra and the carrier thermalization

We report on time-resolved and steady-state photoluminescence studies of GaAs/AlGaAs V-groove quantum wire structures. Steady-state photoluminescence experiments are performed in the temperature range from 8K to 200K. We evaluate the relation between photoluminescence excitation and absorption and determine experimentally an optical density in order to analyze the temperature dependence of the photoluminescence spectra. We find that, at a temperature above 60K, the photoexcited electron-hole pairs reach a thermal equilibrium at the lattice temperature while, at a temperature below about 60K, they do not reach a quasi-equilibrium in the steady-state. Time-resolved photoluminescence studies performed at a carrier density of about 2. 104 cm-1 indicate that, at 60K, a quasi-equilibrium is reached on a time scale of 10 ps. Furthermore, the hot carriers cool in about 100 ps to the lattice temperature. At 8K, however, evidence of a non-thermal carrier distribution is found at the earliest times, which suggests that carriers in extended states are not in thermal equilibrium with carriers in localized states.