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

The notion and usefulness of the effective dielectric constant in sili con nanocrystallites are analyzed using a self-consistent linear scree ning calculation of hydrogenic impurities. It is shown that the self-c onsistent 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 sur face polarization effects. The impurity binding energy, the exciton bi nding energy, and the exchange splitting are estimated taking into acc ount the modified dielectric properties of the crystallites. The conse quences of charging effects on carrier injection are discussed and sho wn to be important.