A simple tight-binding model for deep impurity levels: application to the Jahn-Teller-distorted nitrogen donor in silicon

A cluster-Bethe model for the study of deep impurity levels in a semiconductor is used. The coupling between the donor wavefunction and the lattice distortion is introduced via a dehybridisation mechanism. In addition to the position of the donor deep level and its wavefunction, minimum values of the ionic displacement were evaluated. The resulting stabilization energy is also in good agreement with experiment.