Model based studies of some optical and electronic properties of narrow and wide gap materials

In this presentation, we report our studies of some optical and electronic properties of narrow and wide gap materials. The relevance of the present study in relation to solar cells has also been discussed. These studies are essentially based on the earlier work of Penn,⁽¹⁾ Van Vechten,⁽²⁾ Breckenridgeet al.⁽³⁾ and Grimes and Cowley.⁽⁴⁾ We are then led to a comparative assessment of the various models.^(1-4) Although these models give fair estimates of the Penn gap, it is found that none of them are universally applicable. This has been shown to be especially true for some materials including the alkali halides. Possible reasons for these discrepancies are discussed. In the second part of this work, we present our studies of the temperature and pressure dependence of the Penn gap, energy gap and the high frequency dielectric constant. The electronphonon contribution to the total temperature dependence of (i) the energy gap and (ii) the refractive index is then evaluated. The inverse square law governing the variation of deformation potential with the lattice parameter is seen to be valid for a large number of semiconductors.