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
PCM cell
PCM_0
PCM process
PCM_1
Thermoelectric effects
PCM_2
Thermoelectric SOI device

Publications

  • Okabe, K., Sood, A., Yalon, E., Neumann, C.M., Asheghi, M., Pop, E., Goodson, K.E., Wong, H.-S.P., 2019, "Understanding the Switching Mechanism of Interfacial Phase Change Memory," Journal of Applied Physics, 184501, DOI: 10.1063/1.5093907. READ MORE
  • Guo, P., Burrow, J.A., Sevison, G.A., Sood, A., Asheghi, M., Hendrickson, J.R., Goodson, K.E., Agha, I., Sarangan, A., 2018, "Improving the Performance of Ge2Sb2Te5 Materials via Nickel Doping: Towards RF-Compatible Phase-Change Devices," Applied Physics Letters.113, 171903. READ MORE
  • Shi, L., Dames, C., Likes, J.R., Reddy, P.S., Duda, J., Cahill, D.G., Lee, J., Marconnet, A., Goodson, K.E., Bahk, J.-H., Shakouri, A., Prasher, R.S., Felts, J., King, W.P., Han, B., Bischof, J.C., 2015, "Evaluating Broader Impacts of Nanoscale Thermal Transport Research," Nanoscale and Microscale Thermophysical Engineering, Vol. 19, pp. 127-165. READ MORE
  • Ahn, C., Fong, S., Kim, Y., Lee, S., Sood, A., Neumann, C., Asheghi, M., Goodson, K.E., Pop, E., Wong, H.S.P., 2015, "Energy-Efficient Phase-Change Memory with Graphene as Thermal Barrier," Nano Letters, DOI: 10.1021/acs.nanolett.5b02661 READ MORE
  • Jeyasingh, R., Fong, S., Lee, J., Li, Z., Chang, K.W., Mantegazza, D., Asheghi, M., Goodson, K.E., and Wong, H.S.P., 2014, "Ultrafast Characterization of Phase-Change Material Crystallization Properties in the Melt-Quenched Amorphous Phase," Nano Letters, Vol. 14, pp. 3419-3426 READ MORE
  • Cahill, D.G., Braun, P.V., Chen, G., Clarke, D.R., Fan, S., Goodson, K.E., Keblinski, P., King, W.P., Mahan, G.D., Majumdar, A., Maris, H.J., Phillpot, S.R., Pop, E., and Shi, L., 2014, "Nanoscale Thermal Transport.  II.  2003-2012," Applied Physics Reviews, Vol., 1, 011305. READ MORE
  • Bozorg-Grayeli, E., Reifenberg, J.P., Asheghi, M., Wong, H.-S. P., and Goodson, K.E., 2013, "Thermal Transport in Phase Change Memory Materials," Annual Review of Heat Transfer, Vol. 16, pp. 397-428. READ MORE
  • Lee, J., Bozorg-Grayeli, E., Kim, S., Asheghi, M., Wong, H.-S., and Goodson, K.E., 2013, "Phonon and Electron Transport through Ge2Sb2Te5 Films and Interfaces Bounded by Metals," Applied Physics Letters, Vol. 102, 191911. READ MORE
  • Li, Z., Jeyasingh, R.G.D., Lee, J., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2012, "Electrothermal Modeling and Design Strategies for Multibit Phase Change Memory," IEEE Transactions on Electron Devices, Vol. 59, pp. 3561-3567. READ MORE
  • Ahn, C., Lee, B., Jeyasingh, R.G.D., Asheghi, M., Hurkx, F., and Goodson, K.E., Wong, H.-S.P., 2012, "Effect of Resistance Drift on the Activation Energy for Crystallization in Phase Change Memory," Japanese Journal of Applied Physics, Vol. 51, 02BD06. READ MORE
  • Lee, J., Kodama, T., Won, Y., Asheghi, M., and Goodson, K.E., 2012, "Phase and Temperature Dependent Thermoelectric Properties of Ge2Sb2Te5 Films down to 25 nm Thickness," Journal of Applied Physics, Vol. 112, 014902. READ MORE
  • Ahn, C., Lee, B., Jeyasingh, R.G.D., Asheghi, M., Goodson, K.E., Wong, H.S.P., and Hurkx, G.A.M., 2011, "Crystallization Properties and their Drift Dependence in Phase-Change Memory Studied with a Micro-Thermal Stage," Journal of Applied Physics, Vol. 110, 114520. READ MORE
  • Lee, J., Kim, S., Jeyasingh, R., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2011, "Micro Thermal Stage for Electrothermal Characterization of Phase Change Memory," IEEE Electron Device Letters, Vol. 32, pp. 952-954. READ MORE
  • Lee, J., Li, Z., Reifenberg, J.P., Lee, S., Sinclair, R., Asheghi, M., and Goodson, K.E., 2011, "Thermal Conductivity Anisotropy and Grain Structure in Ge2Sb2Te5 Films," Journal of Applied Physics, Vol. 109, 084902. READ MORE
  • Li, Z., Lee, J., Reifenberg, J.P., Asheghi, M., Jeyasingh, R.G.D., Wong, H.S.P., and Goodson, K.E., 2011, "Grain Boundaries, Phase Impurities, and Anisotropic Thermal Conduction in Phase Change Memory," IEEE Electron Device Letters, Vol. 32, pp. 961-963. READ MORE
  • Kim, S., Lee, B., Asheghi, M., Hurkx, F., Reifenberg, J.P., Goodson K.E., and Wong H.S.P., 2011, "Resistance and Threshold Switching Voltage Drift Behavior in Phase-Change Memory and Their Temperature Dependence at Microsecond Time Scales Studied Using a Micro-Thermal Stage," Transactions on Electron Devices, Vol. 58, pp. 584-592. READ MORE
  • Bozorg-Grayeli, E., Reifenberg, J.P., Panzer, M.A., Rowlette, J.A., and Goodson, K.E., 2011, "Temperature-Dependent Thermal Properties of Phase-Change Memory Electrode Materials," IEEE Electron Device Letters, Vol. 32, pp.1281-1283. READ MORE
  • Bozorg-Grayeli, E.</strong>; Reifenberg, J.P.</strong>; Chang, K.W.; Panzer, M.</strong>; Goodson, K.E</strong>.; , "Thermal conductivity and boundary resistance measurements of GeSbTe and electrode materials using nanosecond thermoreflectance," Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2010 12th IEEE Intersociety Conference on , vol., no., pp.1-7, 2-5 June 2010 doi: 10.1109/ITHERM.2010.5501263 READ MORE
  • Wong, H.S.P., Raoux, S., Kim, S., Liang, J., Reifenberg, J.P., Rajendran, B., Asheghi, M., and Goodson, K.E., 2010, "Phase Change Memory," Proceedings of the IEEE, Vol. 98, pp. 2201-2227. READ MORE
  • Reifenberg, J.P., Chang, K.W., Panzer, M.A., Kim, S., Rowlette, J.A., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2010, "Thermal Boundary Resistance Measurements for Phase-Change Memory Devices," IEEE Electron Device Letters, Vol. 31, pp. 56-58Phonon & Electron Transport at Interfaces READ MORE
  • Reifenberg, J.P., Kencke, D.L., and Goodson, K.E., 2008, "The Impact of Thermal Boundary Resistance in Phase-Change Memory Devices," IEEE Electron Device Letters, Vol. 29, pp. 1112-1114. READ MORE
  • Reifenberg, J.P., Panzer, M.A., Kim, S., Gibby, A.M., Zhang, Y., Wong, S., Wong, H.S., and Goodson, K.E., 2007, "Thickness and Stoichiometry Dependence of the Thermal Conductivity of GeSbTe Films," Applied Physics Letters, Vol. 91, pp. 111904-111906. READ MORE
  • Guo, P.F., Burrow, J.A., Sevison, G.A., Kwon, H., Perez, C., Hendrickson, J.R., Smith, E.M., Asheghi, M., Goodson, K.E., Agha, I., Sarangan, A.M., 2020,  Tungsten-doped Ge2Sb2Te5 phase change material for high-speed optical switching devices," Applied Physics Letters, Vol. 116, 131901. READ MORE
  • Lee, J., Asheghi, M., Goodson, K.E., 2012, "Impact of thermoelectric phenomena on phase-change memory performance metrics and scaling," Nanotechnology, Vol. 23, 205201. READ MORE
  • Lee, J., Kodama, T., Won, Y., Asheghi, M., and Goodson, K.E., 2012, "Phase and Temperature Dependent Thermoelectric Properties of Ge2Sb2Te5 Films down to 25 nm Thickness," Journal of Applied Physics, Vol. 112, 014902. READ MORE
  • Lee, J., Kim, S., Marconnet, A., in t' Zandt, M.A.A., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2012, "Thermoelectric Characterization and Power Generation using a Silicon-on-Insulator Substrate," Journal of MicroElectroMechanical Systems, Vol. 21, pp. 4-6. READ MORE
  • Sevison, G., Farzinazar, S., Burrow, J., Perez, C., Kwon, Heungdong, Lee, J., Asheghi, M., Goodson, K.E., Hendrickson, J., Afha, I., 2020, "Phase Change Dynamics and 2-Dimensional 4Bit Memory in Ge2Sb2Te5 Via Telecom-Band Encoding," ACS Photonics, Vol. 7, pp. 480-487. READ MORE
  • Fong, S.W., Sood, A., Chen, L., Kumari, N., Asheghi, M., Goodson, K.E., Gibson, G.A., and H.S.P. Wong, 2016, "Thermal Conductivity Measurement of Amorphous Dielectric Multilayers for Phase-Change Memory Power Reduction," Journal of Applied Physics, Vol. 120, 015103. READ MORE
  • Won, Y., Lee, J., Asheghi, M., Kenny, T.W., and Goodson, K.E., 2012, "Phase and Thickness Dependent Modulus of Ge2Sb2Te5 Films down to 25 nm Thickness," Applied Physics Letters, Vol. 100, 161905. READ MORE
  • E. Bozorg-Grayeli, J. P. Reifenberg, K. W. Chang, M. Panzer, and K. E. Goodson, "Thermal Conductivity and Boundary Resistance Measurements of GeSbTe and Electrode Materials Using Nanosecond Thermoreflectance", to be appear in the Proceedings of ITHERM, Las Vegas, Nevada, June, 2010. READ MORE
  • Goodson, K.E., 2007, "Ordering up the Minimum Thermal Conductivity of Solids," Science Vol. 315, 342-343. READ MORE