A Model for Charge Transport in Amorphous GST Based on a Modified Variable-Range Hopping Process

Starting from experimental results and first-principle simulations we have developed a transport model for amorphous chalcogenides based upon a hopping process among traps. The conduction mechanism is suitably modeled by means of a generalization of the variable-range hopping, and studied stochastically through Monte Carlo simulations. The transition rates available in the literature have been modified by incorporating the effects of the local electric field. The improved model is able to reproduce the S-shaped current-voltage characteristics of these materials. Simulations have shown that the snap-back effect in the J(V) curve can be ascribed to the formation of domains of opposite charges within the material close to the contact region, acting as a positive feedback for carriers. A microscopic particle description is also used to detect the formation of filaments inside the chalcogenide material.