Recent experimental studies have demonstrated localization of biexcitons in
quantum wells, providing even optical gain up to elevated temperatures. We
present a theoretical treatment of exciton and biexciton states in the wea
k localization limit using a center-of-mass separation ansatz. An advanced
approach based on an extensive numerical solution is compared with a more s
imple model for the quantum well biexciton wave function. Our explicit resu
lts, derived for parameters of the ternary quantum well material (Zn,Cd)Se,
yield that the localization of the biexciton is-despite its larger spatial
extension-stronger than, that of the single exciton state. [S0163-1829(99)
07031-9].