A Local Empirical Pseudopotential Approach to the Optical Properties of SiGe Superlattices.

A reliable empirical pseudopotential method of 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 analytical expression that reproduces correctly a large variety of measured physical data on different scales of reciprocal lattice vectors: bulk band structures, deformation potentials and electron-phonon matrix elements. The present method reproduces the results the first principals microscopic calculations for Si sub n Ge sub 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 situation i.e. different orientations, different stress conditions, different periods, etc... The present approach is therefore a very useful tool for exploring the large parameter space of Si/Ge superlattices.