Electronic structures of semiconductors under pressure

The dielectric constants of semiconductors under pressure are derived from ab initio calculations of the complex dielectric functions epsilon(omega). The pressure coefficient of the refractive index is negative for most tetrahedrally bonded compounds and trends are explained within a simple model. Gap deformation potentials as well as 'absolute' band edge deformation potentials are derived, and the pressure dependence of the electronic structure of superlattices is discussed. Examples from the group III-V, in particular nitrides, and II-VI (ZnS, ZnS/ZnSe) compounds illustrate these investigations. Also, less conventional semiconductors, beta-FeSi2 and epsilon-FeSi, are examined. Strong electron correlation effects limit the validity of LDA theory in these cases. It is suggested that experimental pressure studies can shed new light on the properties of Kondo insulators.