Weak localization of biexcitons in quantum wells

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 weak localization limit using a center-of-mass separation ansatz. An advanced approach based on an extensive numerical solution is compared with a more simple model for the quantum well biexciton wave function. Our explicit results, 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.