Energy Landscape Model of Conduction and Phase Transition in Phase Change Memories

Conduction and switching in the phase-change memory (PCM) strongly depend on the transport mechanisms in the disordered amorphous phase. To predict the programming characteristics and the scaling behavior of PCM, accurate models for transport in the amorphous phase considering the local disorder are essential. This paper presents a numerical model to study the subthreshold conduction in the amorphous state of PCM. The nonhomogeneous active material is described through a potential energy landscape, dictating the local barrier for electron hopping. The model shows strong percolation effects in the amorphous cap of the high resistance state, thus accounting for the observed relationship between the electrical and physical thicknesses of the amorphous cap and for the observed thickness dependence of resistance. The model is finally used to describe the programming characteristics with better accuracy in the transition regime from set to reset, which is critical for multilevel cell applications.