Internal Tamm states in finite and infinite superlattices

Abstract

We study a model of a finite semiconductor superlattice with the last quantum well embedded in contact with an internal potential barrier of arbitrary height. By solving recurrence relations in the envelope-function approximation, we have obtained an explicit equation giving the energy levels of the electronic states. In the infinite limit, it is shown that ``Tamm'' surface states are possible below (or above) critical curves. The Tamm-state energies are computed as a function of the last well width W. Finally, for a finite typical superlattice, the energies of all the electronic modes are shown as a function of the width W.