Electronic Transport Properties of Strained and Relaxed SILICON(1-X) Germanium(x) Alloys

In this thesis, we present a detailed study of the various electronic transport parameters in strained and relaxed Si_{1-x}Ge _{x} alloys. The parameters, viz., the carrier effective mass and mobilities which become tensorial in the strained layer, have been computed following a rigorous treatment of the valence and conduction band structure. In particular, the strained valence band energy spectrum was obtained using k.p perturbation theory coupled with deformation potential theory, suitably taking into account spin-orbit coupling. Exemplary results are also presented for the strained valence band in silicon for purposes of a qualitative verification of the underlying approach. The resulting energy spectrum is fully consistent in terms of its behavior with strain and in relation to the well-established piezoresistive coefficients. The tensorial in-plane and out-of-plane components of hole mobility were both found to increase with increasing Ge fraction regardless of doping concentration. The components of the electron mobility, however, generally degraded with increasing Ge content. The degradation of mobility due to alloy scattering was found to be significantly higher for electrons than holes. The calculated mobility values corroborate well with Monte Carlo simulations and measurement data.