"The role of dopants in the transition temperature of phase change material GeTe"

Phase change material GeTe experiences a resistivity change on the order of a factor of 10⁶ as it changes from amorphous to crystalline upon heating. This change is fast (on the scale of a nanosecond) and repeatable and makes this material a good candidate for high power electronic switching. We perform simulations to model phase change dichalcogenide material GeTe concentrating on the effects of nitrogen dopants on the melting and re-crystallization temperatures. We do this using Density Functional Theory (DFT), and ab-initio Molecular Dynamics (AIMD) to develop a machine-learning motivated Gaussian Approximation Potential. By employing a constant enthalpy simulation at various starting temperatures, we establish a liquid/crystal equilibrium phase that is by construction at the melting temperature and which is in good agreement with experiment. Subsequent calculations gauge the recrystallization temperature as a function of nitrogen dopant concentration with the goal of raising the phase change temperature without sacrificing resistivity change or introducing large volume changes. We explore the underlying mechanism by which the dopants impede recrystallization.