THEORY OF THE CARRIER FERMI ENERGY AND DENSITY OF STATES OF n- and p-TYPE SnTe

In the present work we theoretically develop a k . pi model to calculate the carrier electronic structure for both n- and p-type SnTe. Here pi is the momentum operator in the presence of the spin-orbit interaction. The work is an extension of the theory developed for n- and p-PbTe earlier by one of the authors to evaluate the Fermi energy and the density of states (DOS). We consider a six-level energy basis for SnTe, as proposed by Bernick and Kleinman. One set of calculations was done by diagonalizing the k . pi Hamiltonian matrix for the band-edge states and treating the far bands using perturbation theory. In the second set we have rediagonalized the k . pi Hamiltonian matrix for the band edge states, treating the first diagonalization as the basis. The far bands are, as usual, included through perturbation. We have compared the results of both the sets. Results obtained for n- and p-type SnTe are also compared with that of n- and p-type PbTe. The similarities and contrasts are discussed. An indirect comparison with the DOS of the metallic tin suggests that the calculations are fairly reasonable. The results are also compared with some recent results for SnTe.