TAMM MINIBANDS IN SUPERLATTICES

The properties of interface (Tamm) minibands in a superlattice are investigated in the framework of simple exactly soluble model. In case of nondegenerate bands of constituent materials of the superlattice a couple of Tamm minibands arises from Tamm states localized at the neighboring interfaces, if they exist. It is shown that one can describe these minibands very precisely by means of envelope-function approximation if the boundary conditions take into account the distinctions between band edge Bloch functions of adjacent layers. The case of inverted bands is the only exception, when Tamm states and minibands are not sensitive to the boundary conditions.