Structural changes during the switching transition of chalcogenide selector devices

Abstract

Ovonic threshold switches are a favored choice for chalcogenide-based amorphous (a-) GeSex selector devices used in cross-point arrays of nonvolatile memories. Previous models of their nonlinear high-field conduction proposed a largely electronic-only switching mechanism, within a fixed density of electronic states. Here, we use a density functional molecular-dynamics supercell calculation to show that the high-current excited state configuration of a-GeSex has structural changes such as additional Ge-Ge bonds and overcoordinated Ge sites, giving lower effective mass, more delocalized conduction states, and a lower ON resistance.