  The exciton and biexciton binding energy have been studied for a ZnSe/ZnS
core/shell quantum dot using WKB (Wentzel-Kramers-Brillouin) approximation. The
exciton binding energy increases for small shell thickness and for large
thickness, the binding energy again starts decreasing. A similar result is
obtained for biexcitons where for thicker shells, the biexciton attains
antibonding.
