Improvement of operational stability in SET states of phase-change-type nonvolatile memory devices using Sb-rich phase of Ge–Sb–Te alloys

For realizing the next-generation phase-change memories (PCM), it is required to reduce the fluctuation of resistance values in SET   state. The Sb-rich phase of Ge2Sb2Te5Ge2Sb2Te5 was proposed to fulfill the complete crystallization process at each SET   programming and the PCM devices were fabricated by using the double-layered phase-change materials composed of Ge2Sb2Te5Ge2Sb2Te5 and Ge18Sb39Te43Ge18Sb39Te43. It was found that the SET   resistances and their fluctuation were reduced as the increase of volume ratio of the Ge18Sb39Te43Ge18Sb39Te43. We can conclude that the compositional modification into the Sb-rich phase can be a good way for improving the SET performances for the PCM applications.