Optical gap of P-doped Si nanocrystals

The optical gap of Si nanocrystals strongly doped with phosphorus has been calculated. The energy levels of the electron and hole ground states in the Si nanocrystal were found as functions of the nanocrystal size and the P concentration in the framework of the envelope function approximation and under the assumption of uniform impurity distribution over the nanocrystal volume. It is shown that introducing phosphorus into the nanocrystal leads to a decrease in its optical gap. This decrease is related to a strong shift of the ground electron level produced by the short-range part of the Coulomb electron-P-ion interaction.