HYDROGENIC IMPURITY LEVELS, DIELECTRIC-CONSTANT, AND COULOMB CHARGING EFFECTS IN SILICON CRYSTALLITES

The notion and usefulness of the effective dielectric constant in silicon nanocrystallites are analyzed using a self-consistent linear screening calculation of hydrogenic impurities. It is shown that the self-consistent screened potential induced by the defects can be reasonably approximated by the classical electrostatics expression of the Coulomb potential because the impurity energy levels are dominated by the surface polarization effects. The impurity binding energy, the exciton binding energy, and the exchange splitting are estimated taking into account the modified dielectric properties of the crystallites. The consequences of charging effects on carrier injection are discussed and shown to be important.