A method for calculation of dielectric constants of ultrathin superlattices

An approach to the calculation of static dielectric constants of the (AC)(m)(BC)(n) ultrathin superlattices (SL) composed of III-V or II-VI semiconductors is presented. These SL are formally considered to result from artificial ordering of alternative A (B) atoms in the initial crystalline structure (ICS)-the bulk solid solution A(x)B(1-x)C with x = m/(m + n). According to this viewpoint, the SL dielectric constants are expressed in terms of those of the ICS, and variations depending on the superperiod and degree of ordering. The changes in dielectric constants are calculated on the basis of phenomenological Landau theory of second-order phase transitions, which takes into account thermodynamic instability of the SL. We consider [001]-oriented SL with m + n = 3.