'Current-Striction' - a Mechanism of Electrostriction in Many-Valley Semiconductors

摘要

Electric fields applied to germanium produce deformations which are about 10,000 times as large as those expected from conventional electrostriction mechanisms. A model is presented which does not involve a polarization in real space but, like the current, is mediated by a shift of the electron distribution in reciprocal space. This field-induced shift increases the energy of the electrons within each valley, but the increase is largest in those valleys with smallest effective mass parallel to the field direction. It then becomes energetically favorable for the lattice to deform in such a way that the deformation potential lowers the energy of the high-curvature valleys at the expense of the low-curvature valleys. The magnitude, temperature-dependence, and angular dependence of this effect is calculated for n-type semiconductors. A much smaller effect in silicon than in germanium is found in good agreement with the observed magnitudes. The induced strain is a pure volume-preserving linear dilatation in silicon, whereas it is a pure shear in germanium. (Author)