Bulk zinc-blende lattice semiconductors have the T_d cubic symmetry. For heterostructures CA/C'A' grown along [001] principal axis the point symmetry, of a single interface is reduced to C_2v. The symmetry reduction is due to orientation of planes containing non-standard A-C' or A'-C chemical bonds at the interface. Experiment shows, that in type II structures this induces a remarkable in-plane anisotropy, e.g. vertical photoluminescence in experiments is linearly polarized with the polarization reaching as high values as 80% in case of BeTe/ZnSe [1].

In type II CA/C$'A' systems with large conduction- and valence-band offsets (~2 eV and ~1 eV for BeTe/ZnSe pair) the penetration depth for an electron into the CA layer and for a hole into C'A' layer has the order of the lattice constant.Therefore in such a system the wavefunctions of an electron and a hole participating in the spatially indirect radiative recombination overlap remarkably only over few atomic planes. This property makes the optical matrix element extremely "interface sensitive" and explains the observed high values of linear polarization of the photoluminescence. In this case the validity for the conventional envelope function approximation is questionable and one must instead use microscopical pseudopotential or tight-binding models.

In Ref. [2] we have extended the empiric sp³ tight-binding model in the nearest-neighbor approximation in order to calculate the optical matrix elements and their polarization properties in type II CA/C'A' systems with no-common atom and with large conduction- and valence-band offsets.

In recent years a possibility of hole states localized at a type II interface AlSb/InAs has been under discussion. Moreover, in Ref. [3] calculations of such states are performed in the empirical pseudopotential approach. We have applied the tight-binding model including spin-orbit interactions in order to get localized hole states at AlSb/InAs nterfaces. By extending the theory [2] we describe as well contribution of these localized states to photoluminescence.

1. A.V. Platonov, V.P. Kochereshko, E.L. Ivchenko, G.V. Mikhailov, D.R. Yakovlev, M. Keim, W. Ossau, A. Waag, and G. Landwehr, Phys. Rev. Lett. {83}, 3546(1999)
2. E.L. Ivchenko and M.O. Nestoklon, Zh. Eksper. Teor. Fiz. {121},(2002). [JETP, {94}, 644(2002)].
3. M.J. Shaw, G. Gopir, P.R. Briddon and M. Jaros, J. Vac. Sci. Technol. B {16}, 1794(1998).