Comparison of instantaneous crystallization and metastable models in phase change memory cells

Phase change memory (PCM) is a possible competitor for future generation non-volatile storage class memory due to its fast writing speed and aggressively scaled packing density. In PCM cells current is confined through narrow conductive paths to create high current densities in a chalcogenide material (Ge₂Sb₂Te₅ or GST is most commonly used). The resulting heat allows the material to switch between crystalline (set) and amorphous (reset) states, changing the cell´s resistance by ~10-10⁴ times depending on the cell dimensions. Less energy is required for melting smaller regions, therefore aggressive cell scaling results in reduced power and increased packing density. The properties of GST change by orders of magnitude as a function of temperature, and thus understanding its thermal dependency is crucial to accurately model phase change memory cell operation.