BIEXCITONS IN SEMICONDUCTOR QUANTUM WIRES

We report on spectrally resolved four-wave mixing experiments on InxGa 1-xAs/GaAs quantum wires for a wide range of lateral sizes. Due to the polarization dependence of the four-wave mixing signal, beats in the decay of the signal and an additional emission line in the four-wave m ixing spectrum can be clearly attributed to biexcitons. We find that t he biexciton binding energy depends on both the vertical and lateral d imensions of the wires. For quantum wires with a large vertical confin ement we observe an enhancement of the binding energy of about 40% as compared to a two-dimensional reference sample whereas the biexciton b inding energy is found to be wire.width independent in wires with shal low vertical confinement.