Frontier induced semi-infinite-medium (FISIM) states at semiconductor surfaces and interfaces

Abstract:

In a previous work we have discussed the valence band electronic structure of a (001) oriented surface (semi-infinite medium) of some II-VI wide band gap zinc-blende semiconductor compounds. For these systems, we have found three characteristic surface resonances, besides the known bulk bands (hh, lh and spin-orbit bands). Two of these resonances correspond to the anion terminated surface and the third one to the cation terminated one. We have shown, specifically, that three non dispersive (001)-surface-induced bulk states, in the Γ - X direction of the 2D Brillouin zone, do exist and are characteristic of these systems. The existence of these states has been confirmed, independently, by two experimental groups and further evidence of our predictions has been more recently found. In order to continue with the description of these states, in this work, we briefly review the main characteristics of the electronic structure of the (001)-surfaces to up-date their analysis and we present new results concerning the existence of the same kind of states in Cu-based calcopyrites and at interfaces. This shows that, in general, the non-dispersive states occur in several, if not all, crystal surfaces, and, on general grounds, as the consequence of introducing to an infinite medium a frontier of any kind (not only with the vacuum). For that reason we propose here, to name them, more appropriately as Frontier Induced Semi-Infinite Medium (FISIM) states. We present in this paper two new interesting cases where the non-dispersive states appear. First, the (112)-oriented CuInSe₂ calcopyrite surface and, secondly, the interface CdTe/CdSe_xTe_1-x (x = 0.15) which, essentially, does not introduce the additional effects due to lattice mismatch so that the FISIM states are clearly seen. We have calculated them for a broader range of x and for other II-VI and III-V semiconductor compounds to check that the result is general. The surface and the interface that we present here, allow us to discuss the characteristics of these newly found states, in a more general way.