Rapid relaxation of hot carriers in GaAs fractional-layer superlattice quantum wires

We measure the hot carrier relaxation in two GaAs quantum wire arrays made from fractional-layer superlattices (FLS). Using femtosecond optical pump-probe spectroscopy, we measure the differential transmission spectra for various pump-probe time delays from which we determine the carrier thermalization times. Although the two FLS structures have different degrees of one-dimensional confinement at the band edge, we observe rapid (<2 ps) and efficient carrier relaxation in both cases with no sign of the inhibited relaxation predicted for ideal one-dimensional structures. We believe that FLS quantum wife structures avoid relaxation bottlenecks because the shape of the FLS confinement potential produces high energy states which are two dimensional in character and which facilitate rapid energy relaxation. (C) 1996 American Institute of Physics.