Electric field dependence of conductivity in thin amorphous films and bulk glasses of the system Ge 4Se 6−xTe x

Abstract

The electric field dependence of the conductivity of amorphous Ge 4Se 6− x Te x ( x = 0, 0.5, 1.0 or 1.5) is strongly influenced by the way in which the samples are prepared. Bulk samples are compared with thin films of identical composition prepared by vacuum evaporation at relatively low temperature or by flash evaporation. Differences in the shape of the field dependence of the conductivity are discussed in terms of a conductivity model which takes into account the Poole-Frenkel effect with intrinsic defects of the valence alternation pair type and hopping contributions from charge transport via localized states at the band edges. It is shown that the preparation technique influences the density of intrinsic defects and localized states at the band edges resulting in a different field dependence of the conductivity.