Electrical Switching Properties of Ternary and Layered Chalcogenide Phase-Change Memory Devices

Due to the increasing demand for products which use Non-Volatile Memory (NVM) and the near realization of the scaling limits of Flash [1, 2], a large research effort is underway. This effort is to develop new forms of NVM capable of replacing Flash [3]. At the forefront of this research is Phase-Change Random Access Memory (PCRAM). Chalcogenide based PCRAM is one of the most promising non-volatile memories for the next generation of portable electronics, due to its excellent scalability, large sensing margin, fast switching speed, and possible multi-bit per cell operation [3]. It is desirable for a phase-change random access memory (PCRAM) device to achieve multiple resistance states in order to find application in analog logic circuits and reconfigurable electronics, as well as in radiation hardened high-density memories. To explore the possibility of achieving multiple resistance states in a PCRAM device, we have performed electrical measurements on devices comprised of at least two layers of chalcogenide material. One of the layers is either SnSe or SnTe and the other layer is either GeTe or Ge2Se3. We compare the room temperature operation of the Layered devices to the devices fabricated with single layered Ternary samples consisting of the following compositions: (Ge2Se3) 97Sn3, (Ge 2Se3)97Zn3, (Ge2Se3)97Sb3, or (Ge2Se3)97In3