Electronic structure of PbSnMnTe at high carrier densities Original Research Article

An improved ( being the momentum operator in the presence of spin–orbit interaction) theory is developed to take care of the electronic structure of degenerate narrow-gap lead salt semiconductors at high densities. The usual procedure of treating the band edge levels exactly and the far bands using perturbation theory does not work well beyond carrier densities of about 1018 cm−3. The convergence in a self-consistent calculation is poor beyond this range. As an improvement, we extend the model by rediagonalizing the band-edge Hamiltonians. The resulting states are then treated with the far bands using perturbation theory. The theory is applied to the diluted magnetic semiconductor, PbSnMnTe, in view of the importance of carriers at high density in understanding certain magnetic properties of this material. As a first step, we calculate the electronic structure of PbSnMnTe in the non-magnetic case and present our results for the Fermi energy and the density of states of degenerate holes. The convergence appears to be satisfactory up to about a carrier density of 1020 cm−3 in p-Pb1−x−ySnxMnyTe. Comparisons between new and old results are made, which clearly underscore the advantage of the new model.