SURFACE LOCALISED STATES IN SEMICONDUCTOR SUPERLATTICES

Abstract

We study models of finite and semi--infinite semiconductor superlattices with embedded well(s) of arbitrary width, adjacent to the internal potential barrier(s) of arbitrary heights. By solving recurrence relations in the envelope-function approximation, we have obtained explicit equations giving the energy levels of the electronic states. ln the infinite limit., it is shown that "Tamm" surface states are possible below (or above) critical curves. The Tamm-state energies and computed as a function of the surface well and for some typical finite superlattices, the energies of all the electronic modes are shown as a function of the surface well width. Models with a centrally modes are shown as a function of the surface well width. Models with a centrally embedded well within the superlattice with finite and infinite asymmetric well structures are also studied, showing the existence of localised states. We also study the effect of an external field upon the bound electronic states using an exact Airy solution method.