A tight-binding description of isovalent impurity clusters

For centres of several Te substitutionals in nearest-neighbour anion position in the host crystals ZnS, ZnSe, CdS, and CdSe a tight-binding description is given. The matrix of the Hamiltonian in the sp3-representation includes all interactions up to the second-nearest neighbours and is based upon a charge self-consistent parametrization. All Te centres suitable in a tetrahedrally coordinated five-atom cluster are considered. Using the Koster-Slater scattering theory the off-diagonal matrix elements of the impurity potential have to be included. Thereby the results of the calculation are in a good agreement with experimental data for the energy levels of complex Te impurities in II-VI semiconductors. (author)