Local empirical pseudopotential approach to the optical properties of Si/Ge superlattices

Abstract

A reliable empirical pseudopotential method for computing the near-gap band structures and optical matrix elements of strained Si/Ge superlattices has been developed. The pseudopotentials of Si and Ge are represented by an analytic expression that reproduces correctly a large variety of measured physical data on different scales of reciprocal-lattice vectors particularly in the G→0 limit: bulk band structures, deformation potentials, electron-phonon matrix elements, and heterostructure valence-band offsets. The present method reproduces the results of first-principles microscopic calculations for ${\mathrm{Si}}_{\mathrm{n}}$ ${\mathrm{Ge}}_{\mathrm{n}}$/Si(001) superlattices with n=2, 4, and 6 within 0.1 eV in the near-gap region. The method allows the exploration of a wide variety of situations, i.e., different orientations, different stress conditions, and different periods.