Energy Bandpass Filtering in Superlattice Phase Change Memories.

We propose energy bandpass filtering employed using the idea of antireflection heterostructures as means to reduce the energy requirements of a superlattice phase change memory (PCM) based on germanium telluride (GeTe) and Sb2Te3 heterostructures. Different configurations of GeTe/Sb2Te3 superlattices are studied using the nonequilibrium Green’s function approach. Our electronic transport simulations calculate the coupling parameter for the high-resistance covalent state, to 97% that of the stable low-resistance resonant state, maintaining the ON/OFF ratio of 100 for a reliable read operation. By examining various configurations of the superlattice structures, we conclude that the inclusion of antireflection units on both sides of the superlattice increases the overall ON/OFF ratio by an order of magnitude which can further help in scaling down of the memory device. It is also observed that the device with such antireflection units exhibits 32% lesser RESET voltage than the most common PCM superlattice configurations. Moreover, we also find that the ON/OFF ratio in these devices is also resilient to the variations in the periodicity of the superlattice. [ABSTRACT FROM AUTHOR]