DIELECTRIC PROPERTIES OF SEMICONDUCTORS

Abstract

In this thesis, we have studied the dielectric properties of semiconductors. The quantity of interest is the wave vector q and frequency go-dependent macro-scopic dielectric function e(i,co). We confine ourselves to small q values, since in this range the dielectric response of semiconductors differs significantly from that of metals. To calculate the dielectric properties of semiconductors, we have used the simple model approach. For the major part of this study, the Penn model has been used. This is a two band nearly-free-electron model, isotropically extended in three dimen-sions. The model assumes a constant. energy gap at the Jones' zone. The work of Heine and. Jones has shown that the energy gap does indeed remain constant over the surface of Jones' zone except along symmetry direc-tions. This lends sup1ort to the Penn model and suggests its use for realistic calculations. To see the effects of band structure on the various dielectric properties, we have also used a model band structure proposed by Milchev. Our studies of the dielectric properties are motivated by (i) the inherent simplicity in the analytic expressions for various dielectric properties (ii) show-ing the explicit dependence, of these properties on the . band parameters (iii) the ability to give a reasonable agreement with experimental data...