Electric-field–induced electron density response of GaAs and ZnSe

The response of the electron densities of GaAs and ZnSe to an external electric field was probed by measuring the variation of the integral intensity of several weak X-ray structure factors due to a field parallel to [1 1 1]. In the range − 3 kV/mm < E < + 3 kV/mm we found a nearly linear dependence of the relative intensity variation Δ R / R on E for low indexed reflections (2 2 2, 0 6 0) and an additional E 2 -dependence for higher-indexed ones (4 4 2, 6 6 6). The results are interpreted in terms of a bond-charge model. The linear effect can be interpreted by the redistribution of valence charges from bonds parallel to E into bonds lying oblique (bond-charge transfer) whereas the origin of the non-linear effect is still unclear. After the exclusion of lattice effects (piezo-electric effect, internal strain) it ought to be allocated to a charge density response of the core region.