Time resolved magneto-spectroscopy of InGaAs/GaAs V-shaped quantum wires

We present a continuous-wave and time-resolved magnetoluminescence investigation of InxGa1-xAs V-shaped quantum wires (QWR's) with In content x = 0.1, 0.15, 0.2. The diamagnetic shifts and the field dependence (up to 8 T) of the recombination lifetime show a competition between exciton and free-carrier processes. In QWR's with low In content (x = 0.1) the observed increase of the photoluminescence decay time with the magnetic field is explained by a theoretical calculation of free-carrier recombination. In-rich QWR's exhibit instead a decrease of the decay time at low temperature, which is characteristic of the exciton recombination, and an increase at high temperatures when thermal ionization of excitons occurs. Our results indicate that the extent to which exciton or free-carrier recombination predominates depends on the temperature and on the strength of the built-in piezoelectric field.