Ab initio study of electromigration in liquid GeAsSe alloys for selector devices

Selenide amorphous alloys are of interest for applications in selector devices that exploit a sort of reversible dielectric breakdown called ovonic threshold switching. In the on-state of the device, the system is typically brought into the supercooled liquid phase above the glass transition temperature, where the atomic mobility is sufficiently high to cause demixing driven by the electric field. The electromigration force F responsible for ionic migration is proportional to the electric field E via the effective charge Z* (F = |e|Z*E, where e is the electron charge), which is thus of great relevance for the electrothermal modeling of the devices. In this work, we computed Z* for a prototypical GeAsSe selector alloy by leveraging a non-equilibrium Green’s function method based on density functional theory. The effective charges in the metallic liquid were obtained by calculating the atomic forces, including the wind force, in the presence of both an electric field and an electronic current.