Dynamics of exciton relaxation in GaAs V-shaped quantum wires

We present a systematic investigation of continuous wave and transient photoluminescence in GaAs V-shaped quantum wires as a function of the excitation intensity, the excess energy of the exciting probe, and the sample temperature. Exciton localization is observed at low temperatures. Free exciton polariton transitions are monitored at intermediate temperatures through the square root temperature dependence of the decay time. At high excitation densities band filling, fast relaxation of the higher subband and slow intersubband relaxation (about 900 ps) is observed. An oscillatory behavior of the ground state decay time as a function of the excitation energy is observed in all samples. It can be explained by a modulated carrier collection efficiency into the QWires by means of a cascade of LO-phonon scattering.