THE EFFECT OF INTERFACE ROUGHNESS SCATTERING AND BACKGROUND IMPURITY SCATTERING ON THE THERMOPOWER OF A 2DEG IN A SI MOSFET

For a 2DEG in a Si MOSFET the important scattering mechanisms at low temperatures are remote impurity, background impurity and interface roughness scattering. We perform a detailed calculation of the energy dependence of each scattering mechanism in the extreme quantum limit with a view to explaining the observed electron concentration dependence of the thermopower. For N(s) less than 8 X 10(15) m-2, scattering by remote impurities dominates. A change of sign of the diffusion thermopower is predicted at low T and high N(s), due to the dominance of scattering by background impurities and interface roughness. The total thermopower is calculated by including the phonon drag contribution, the result being in satisfactory agreement with experimental data.