Sponsors: NSF, Intel, NXP, Ovonyx, SRC
Collaborators: H.S.P. Wong group, Stanford EE
Students: Dr. Joe Katz, Dr. Aditya Sood

Phase change memory (PCM or PCRAM) is based on rapid, thermally-induced phase transitions in Ge2Sb2Te5 (GST) and related compounds. Because the phase change is induced by temperature changes, thermal conduction and thermally-induced phase transitions govern the critical device figures of merit including the time and energy required for switching. PCRAM is now available commercially in memory products, and is arguably the most promising technology for ultra-high-density nonvolatile storage in the coming decades.

Stanford has built the world leading team for PCM investigations with a focus on the fundamental physics governing electrical, thermal and electrothermal transport phenomena. Progress includes detailed characterization of the thermal and electrical conductivities of GST as a function of material stoichiometry and grain orientation and size (crystalline phase), as well as the first studies revealing the interface resistance magnitudes and their impact in devices. Ongoing and future work is focused on the multibit storage challenge with associated fundamental activities on temperature-induced drift in reset resistance and threshold voltage enabled by our novel micro thermal stage (MTS). We are also characterizing the thermoelectric properties of GST layers as well as the thermal and thermoelectric properties of GST nanowires.

This material is based upon work supported by the National Science Foundation under Grant No. CBET-0853350. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

PCM cell
PCM process
Thermoelectric effects
Thermoelectric SOI device