Clustering model in N-doped many-valley semiconductors

The microscopic structure of the impurity states in n-silicon as an example of randomly distributed donor impurities in a diamond structure many-valley semiconductor is investigated. An improved Hartree-Fock-Roothaan scheme with spin-polarized potentials and a Kohn-Luttinger donor wave function associates with each impurity were used in the calculation. It is shown that the many-valley character of the host gives rise to a distribution of impurity clusters of various sizes, quite different from the case of neglecting the valley multiplicity, and that is strongly reduces the self-compensation effect due to the potential fluctuation. The results are in agreement with recent investigations that have appeared in the literature. (Author)