Coherent spectroscopy of semiconductor quantum wires

In0.135Ga0.865As/GaAs quantum wires with widely varying widths down to 29 nm have been studied by degenerate four-wave mixing. The exciton binding energy EB in the wires has been determined by quantum beat spectroscopy. We find an increase of EB with decreasing wire width, giving clear evidence for the lateral confinement of the excitons in the wire structures. Further, the exciton dephasing kinetics due to exciton-phonon and exciton-exciton scattering is studied. For both dephasing mechanisms we find an increase of the scattering rates with decreasing wire width. For the exciton-phonon scattering the increase is rather weak, while for the exciton-exciton scattering a drastic increase of the scattering rate is observed.