BIEXCITON FORMATION BY 2-PHOTON ABSORPTION IN QUANTUM-WELLS

Direct creation of biexciton states by two-photon absorption in quantum well struture semiconductors is investigated theoretically. The two-photon transition rate to biexciton as a final state is analytically calculated for both photon polarization configurations. The biexciton matrix element has been estimated adopting a more accurate variational parameters wave function. A numerical application for GaAs Quantum Well (QW) shows that the biexciton two-photon absorption coefficient, alpha(2) (biex) for both polarizations is enhanced over the exciton two-photon absorption coefficient, alpha(2) (ex), by an order of magnitude. This enhancement is, essentially, found to arise from a resonance effect and the structure of the matrix elements involved in the two processes. Furthermore, alpha(2) (biex), in a GaAs QW is four order of magnitude larger than alpha(2)(biex) in bulk GaAs. This large increase is due to the spatial confinement of the carriers in the QW.