Magnetoresistance of a silicon Mosfet on the (111) surface in a parallel magnetic field

In comparison with silicon (100) we argue that the silicon (111) surface is a surface with higher mobility and stronger Coulomb interaction effects. For the resistance of the two-dimensional electron gas we discuss the effects of a magnetic field parallel to the surface: for zero temperature we present theoretical results for the magnetoresistance of an electron gas at the surface of silicon (111) with a six-fold valley degeneracy. Impurity scattering and interface roughness scattering are taken into account. A recent study of a hydrogen-passivated silicon (111) surface showed a mobility proportional to the electron density. We present, using a model for neutral impurities, predictions for the magnetoresistance of this sample in a parallel magnetic field.