Schmid U., Christensen N.E., Cardona M.
The authors present relativistic (including spin) linear muffin-tin orbitals (LMTO) calculations of the band structure of Si, Ge and zinc-blende-like GeSi. The errors in excitation energies introduced by the use of the local-density approximation to the exchange-correlation potential are corrected with 'ad hoc' potentials placed at the atomic sites. Effective masses, matrix elements of p, and Luttinger parameters are evaluated. Special emphasis is placed on the effects of inversion asymmetry in GeSi, such as ionicity and spin splittings. The former is very small, probably with Ge acting as the cation. The latter are appreciable and can be related to the asymmetry in the spin-orbit splittings of both constituent atoms. A detailed study of these spin splittings is made, also with the help of k.p perturbation theory. The coefficients of terms linear and cubic in k around k=0 are obtained. They should be experimentally observable when high-quality samples become available and should help to understand similar splittings in (Ge)n/(Si)m (n,m odd) superlattices.
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