EFFECTIVE DIELECTRIC RESPONSE OF SEMICONDUCTOR COMPOSITES

Using a previously proposed diagrammatic approach for the calculation of the renormalized polarizability of spherical inclusions in a homoge neous matrix we obtain an effective dielectric response of a composite of nonpercolating inclusions taking into account a continuous distrib ution of sizes of the spheres. We apply this theory to semiconductor-d oped glasses (SDG) calculating both the electron and phonon responses in the far-infrared and optical spectral regions, respectively, and al so to a strongly inhomogeneous semiconductor alloy. For SDG, we compar e our calculated results with available experimental data on interband optical absorption and obtain good agreement by choosing the appropri ate distribution function of sizes of the spheres. In the case of the C(d)xHg(1-x)Te alloy, we find an interesting interplay of the composit e effects and phonon-plasmon coupling resulting in a rich structure fo r the reflectivity spectra. We compare these results to those calculat ed using another approach, which is widely used for describing the die lectric properties of composites, the self-consistent approximation, a nd discuss the relation between the two approaches.