Threshold switching in chalcogenide-glass thin films

We discuss bias-induced threshold switching in chalcogenide-glass thin films, with an emphasis on the unique aspects of this phenomenon. The electronic nature of both the ON state and the recovery process is now clear. In this paper, we also establish the fundamentally electronic origin of the initiation process. An isothermal model is presented and analyzed for filamentary ON-state solutions via a set of phenomenological kinetic equations consistent with recent advances in our understanding of the electronic structure of chalcogenide glasses. The predictions of this model compare favorably with a variety of experimental results. The model is basically that the switching transition develops when a critical electric field is reached somewhere in the sample, usually near an electrode. Field-induced carrier generation then causes the charged traps in the bulk to fill (neutralize). When all the traps are filled, carriers can transit the sample with an enhanced mobility and the generation rate required to keep the traps filled is reduced from its threshold value.