Carrier relaxation in GaAs v-groove quantum wires and the effects of localization

Carrier relaxation processes have been investigated in GaAs/AlxGa1−xAs v-groove quantum wires (QWRs) with a large subband separation sDE.46 meVd. Signatures of inhibited carrier relaxation mechanisms are seen in temperature-dependent photoluminescence (PL) and photoluminescence-excitation measurements; we observe strong emission from the first excited state of the QWR below ,50 K. This is attributed to reduced intersubband relaxation via phonon scattering between localized states. Theoretical calculations and experimental results indicate that the pinch-off regions, which provide additional two-dimensional confinement for the QWR structure, have a blocking effect on relaxation mechanisms for certain structures within the v groove. Time-resolved PL measurements show that efficient carrier relaxation from excited QWR states into the ground state occurs only at temperatures *30 K. Values for the low-temperature radiative lifetimes of the groundand first excited-state excitons have been obtained (340 ps and 160 ps, respectively), and their corresponding localization lengths along the wire estimated.