Modeling of two different operation modes of phase change material for phase-change random-access memory

Two basic models for phase-change random-access memory (PRAM) are compared for the first time. Model I is based on polycrystalline Ge2Sb2Te5, and the phase change takes place only in some of the film. Model 2 is based on amorphous Ge2Sb2Te5. This work indicates that model I has an excellent R-OFF/R-ON, but inferior structure and reset current. Model 2 has superior structure and reset current, but inferior R-OFF/R-ON. Therefore, for model 2, it is important to control the thickness of nonprogrammable volume to ensure sufficient R-OFF/R-ON and the proper range of the ratio of non-programmable volume and programmable volume is calculated as 0.003-1%. The simulation result shows the temperature distribution of model 2 can satisfy the actual requirement well, and the reset current can be reduced to 0.15 mA, much lower than that in model 1.