Enhancement of binding energies and polarized emission of 0D biexcitons

The energy states of quasi zero-dimensional biexcitons are studied in epitaxially grown CdS/ZnS quantum structures. Selecting a semiconductor structure with high bulk exciton energy, comparatively small ratio in effective masses and strong 3D quantum confinement, an engineering of biexciton binding energies was possible towards highest values even exceeding the bulk exciton Rydberg energies. At low temperatures, the biexciton–phonon interaction is dominated by coupling to acoustic phonons. A strong enhancement of exchange splitting effects is observed resulting in two linearly polarized exciton peaks. The unusual preference polarization of the biexciton emission is attributed to a relaxation of selection rules because of anisotropies in the confining potentials and mixing of valence band states