Spectroscopy of bound excitons in cubic ZnS at moderate to high excitation densities

We report on luminescence and excitation spectroscopy of bound excitons in cubic ZnS for moderate to high incident-light intensities. For the first time, the electronic fine structure of the ground state of the acceptor-exciton complex could be analyzed for two different acceptor centers, one of them being due to an iodine-related impurity. The electronic states of the complexes give rise not only to pronounced excitation resonances but also to intense resonant Raman scattering. For increasing excitation densities, the bound excitons are shown to remain the dominant excitonic feature in cubic ZnS until, for more than 100 kW/${\mathrm{cm}}^2$, a broadband emission begins to cover the whole investigated range; this emission is most probably due to electron-hole–drop creation.