Biexciton binding energy in spherical quantum dots with $\Gamma_{8}$ valence band

The biexciton binding energy in spherical CdSe/ZnSe quantum dots is calculated variationally in the framework of $k$ $p$-perturbation theory. Smooth and abrupt confining potentials with the same localization area of carriers are compared for two limiting cases of light hole to heavy hole mass ratio $\beta$ = mlh/mhh: $\beta$ = 1 and $\beta$ = 0. Accounting for correlations between carriers results in their polarized configuration and significantly increases the biexciton binding energy in comparison with the first order perturbation theory. For $\beta$ = 0 in smooth confining potentials there are three nearby biexciton states separated by small energy gap between 1$S3/2$ and 1$P3/2$ hole states.