Distortion of Energy Surfaces by a Strain Field

Deformation of energy bands in solids in the presence of a strain field is discussed from a symmetry point of view. The very particular case of the conduction band of silicon in an orthorhombic strain is examined in some detail. The distortion of the energy surface in this case gives rise to an additional contribution to piezoresistance and predicts the correct sign and magnitude of the piezoresistance coefficient 11"44, which has been predicted to vanish by the conventional electron transfer theory.