THERMAL IONIZATION OF EXCITONS IN V-SHAPED QUANTUM WIRES

The exciton-to-free-carrier transition in GaAs and InxGa1-xAs V-shaped quantum wires is revealed by means of temperature-dependent magnetolu minescence experiments. The experimental results are in excellent agre ement with the diamagnetic shift obtained from a solution of the full two-dimensional Schrodinger equation for electrons and holes including magnetic-held and excitonic effects. In the GaAs wires, the exciton-t o-free-carrier transition is found to occur at temperature consistent with the exciton binding energies. In the InxGa1-xAs wires the diamagn etic shift of the luminescence is found to be free-carrier-like, indep endent of temperature, due to the weakening of the exciton binding ene rgy induced by the internal piezoelectric field.