Journal of Computational Electronics

, Volume 13, Issue 3, pp 620–626 | Cite as

Role of inelastic electron–phonon scattering in electron transport through ultra-scaled amorphous phase change material nanostructures

  • Jie Liu
  • Xu Xu
  • M. P. Anantram


The electron transport through ultra-scaled amorphous phase change material (PCM) GeTe is investigated by using ab initio molecular dynamics, density functional theory, and non-equilibrium Green’s function, and the inelastic electron–phonon scattering is accounted for by using the Born approximation. It is shown that, in ultra-scaled PCM device with 6 nm channel length, \(<\)4 % of the energy carried by the incident electrons from the source is transferred to the atomic lattice before reaching the drain, indicating that the electron transport is largely elastic. Our simulation results show that the inelastic electron–phonon scattering, which plays an important role to excite trapped electrons in bulk PCM devices, exerts very limited influence on the current density value and the shape of current–voltage curve of ultra-scaled PCM devices. The analysis reveals that the Poole–Frenkel law and the Ohm’s law, which are the governing physical mechanisms of the bulk PCM devices, cease to be valid in the ultra-scaled PCM devices.


Phase change material Non-equilibrium Green’s function (NEGF) Electron phonon scattering Mean free path (MFP) Ultra-scaled nanostructure 



This work was supported by U.S. National Science Foundation (NSF) under Grant Award 1006182. We acknowledge the Pacific Northwest National Laboratory (PNNL) for providing computational resources on the PNNL Chinook supercomputers. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant number OCI-1053575. This work was facilitated through the use of advanced computational, storage, and networking infrastructure provided by the Hyak supercomputer system, supported in part by the University of Washington’s eScience Institute. We acknowledge J. Akola and R.O. Jones (for discussion about AIMD simulations).


  1. 1.
    Liu, J., Anantram, M.P.: Low-bias electron transport properties of germanium telluride ultrathin films. J. Appl. Phys. 113(1–6), 063711 (2013)CrossRefGoogle Scholar
  2. 2.
    Liu, J., Xu, X., Anantram, M.P.: Sub-threshold electron transport properties of ultra-scaled phase change memory. IEEE Electron Device Lett. 35(5), 533–535 (2014). doi: 10.1109/LED.2014.2311461 CrossRefGoogle Scholar
  3. 3.
    Liu, J., Xu, X., Brush, L., Anantram, M.P.: A multi-scale analysis of the crystallization of amorphous germanium telluride using ab-initio simulations and classical crystallization theory. J. Appl. Phys. 115(1–7), 023513 (2014)CrossRefGoogle Scholar
  4. 4.
    Liu, J., Yu, B., Anantram, M.P.: Scaling analysis of nanowire phase-change memory. IEEE Electron Device Lett. 32, 1340–1342 (2011)CrossRefGoogle Scholar
  5. 5.
    Liu, J., Yu, B., Anantram, M.P.: Isotropic and anisotropic scaling analysis of nanowire phase change memory. 11th IEEE Conference on Nanotechnology, pp. 1343–1347 (2011)Google Scholar
  6. 6.
    Raoux, S., Wuttig, M. (eds.): Phase Change Materials Science and Applications. Springer, New York (2009)Google Scholar
  7. 7.
    Ielmini, D.: Threshold switching mechanism by high-field energy gain in the hopping transport of chalcogenide glasses. Phys. Rev. B 78(1–8), 035308 (2008)CrossRefGoogle Scholar
  8. 8.
    Ielmini, D., Zhang, Y.G.: Analytical model for subthreshold conduction and threshold switching in chalcogenide-based memory devices. J. Appl. Phys. 102(1–13), 054517 (2007)CrossRefGoogle Scholar
  9. 9.
    Ielmini, D., Zhang, Y.G.: Evidence for trap-limited transport in the subthreshold conduction regime of chalcogenide glasses. Appl. Phys. Lett. 90(1–3), 192102 (2007)CrossRefGoogle Scholar
  10. 10.
    Kim, S.B., Bae, B.J., Zhang, Y., Jeyasingh, R.G.D., Kim, Y., Baek, I.G., Park, S., Nam, S.W., Wong, H.-S.P.: One-dimensional thickness scaling study of phase change material(Ge2Sb2Te5) using a pseudo 3-terminal device. IEEE Trans. Electron Device 58, 1483–1489 (2011)CrossRefGoogle Scholar
  11. 11.
    Simpson, R.E., Krbal, M., Fons, P., Kolobov, A.V., Tominaga, J., Uruga, T., Tanida, H.: Toward the ultimate limit of phase change in Ge2Sb2Te5. Nano Lett. 10, 414–419 (2010)CrossRefGoogle Scholar
  12. 12.
    Caldwell, M.A., Raoux, S., Wang, R.Y., Wong, H.-S.P., Milliron, D.J.: Synthesis and size-dependent crystallization of colloidal germanium telluride nanoparticles. J. Mater. Chem. 20, 1285–1291 (2010)CrossRefGoogle Scholar
  13. 13.
    Raoux, S., Jordan-Sweet, J.L., Kellock, A.J.: Crystallization properties of ultrathin phase change films. J. Appl. Phys. 103(1–7), 114310 (2008)CrossRefGoogle Scholar
  14. 14.
    Raoux, S., Rettner, C.T., Jordan-Sweet, J.L., Deline, V.R., Philipp, J.B., Lung, H.L.: Scaling properties of phase change nanostructures and thin films. Proc. Euro. Symp. on Phase Change and Ovonic Science, pp. 127–134 (2006)Google Scholar
  15. 15.
    Wong, H.-S.P., Kim, S., Lee, B., Caldwell, M.A., Liang, J.L., Wu, Y., Jeyasingh, R.G.D., Yu, S.M.: Recent progress of phase change memory (PCM) and resistive switching random access memory (RRAM). 10th IEEE International Conference on Solid-State and Integrated Circuit Technology, pp. 1055–1060 (2010)Google Scholar
  16. 16.
    Wong, H.-S.P., Raoux, S., Kim, S., Liang, J.L., Reifenberg, J.P., Rajendran, B., Asheghi, M., Goodson, K.E.: Phase change memory. Proc. IEEE 98, 2201–2227 (2010)CrossRefGoogle Scholar
  17. 17.
    Burr, G.W., Breitwisch, M.J., Franceschini, M., Garetto, D., Gopalakrishnan, K., Jackson, B., Kurdi, B., Lam, C., Lastras, L.A., Padilla, A., Rajendran, B., Raoux, S., Shenoy, R.S.: Phase change memory technology. J. Vac. Sci. Technol. B 28, 223–262 (2010)CrossRefGoogle Scholar
  18. 18.
    Raoux, S., Burr, G.W., Breitwisch, M.J., Rettner, C.T., Chen, Y.C., Shelby, R.M., Salinga, M., Krebs, D., Chen, S.H., Lung, H.L., Lam, C.H.: Phase-change random access memory: a scalable technology. IBM J. Res. Device 52, 465–479 (2008)CrossRefGoogle Scholar
  19. 19.
    Lee, T.H., Elliott, S.R.: Structural role of vacancies in the phase transition of Ge2Sb2Te5 memory materials. Phys. Rev. B 84(1–5), 094124 (2011)CrossRefGoogle Scholar
  20. 20.
    Lee, T.H., Elliott, S.R.: Ab initio computer simulation of the early stages of crystallization: application to Ge2Sb2Te5 phase-change materials. Phys. Rev. Lett. 107(1–5), 145702 (2011)CrossRefGoogle Scholar
  21. 21.
    Hegedus, J., Elliott, S.R.: Microscopic origin of the fast crystallization ability of Ge–Sb–Te phase-change memory materials. Nat. Mater. 7, 399–405 (2008)Google Scholar
  22. 22.
    Krbal, M., Kolobov, A.V., Fons, P., Tominaga, J., Elliott, S.R., Hegedus, J., Uruga, T.: Intrinsic complexity of the melt-quenched amorphous Ge2Sb2Te5 memory alloy. Phys. Rev. B 83(1–8), 054203 (2011)CrossRefGoogle Scholar
  23. 23.
    Akola, J., Jones, R.O.: Structural phase transitions on the nanoscale: The crucial pattern in the phase-change materials Ge2Sb2Te5 and GeTe. Phys. Rev. B 76(1–10), 235201 (2007)CrossRefGoogle Scholar
  24. 24.
    Akola, J., Jones, R.O.: Density functional study of amorphous, liquid and crystalline Ge2Sb2Te5: homopolar bonds and/or AB alternation. J. Phys. Condens. Matter 20(1–10), 465103 (2008)CrossRefGoogle Scholar
  25. 25.
    Akola, J., Jones, R.O.: Binary alloys of Ge and Te: order, voids, and the eutectic composition. Phys. Rev. Lett. 100(1–4), 205502 (2008)CrossRefGoogle Scholar
  26. 26.
    Akola, J., Jones, R.O., Kohara, S., Kimura, S., Kobayashi, K., Takata, M., Matsunaga, T., Kojima, R., Yamada, N.: Experimentally constrained density-functional calculations of the amorphous structure of the prototypical phase-change material Ge2 Sb2 Te5. Phys. Rev. B 80(1–4), 020201 (2009)CrossRefGoogle Scholar
  27. 27.
    Akola, J., Jones, R.O.: Structure of amorphous Ge8Sb2Te11: GeTe-Sb2Te3 alloys and optical storage. Phys. Rev. B 79(1–8), 134118 (2009)CrossRefGoogle Scholar
  28. 28.
    Akola, J., Larrucea, J., Jones, R.O.: Polymorphism in phase-change materials: melt-quenched and as-deposited amorphous structures in Ge2Sb2Te5 from density functional calculations. Phys. Rev. B 83(1–7), 094113 (2011)CrossRefGoogle Scholar
  29. 29.
    Kalikka, J., Akola, J., Larrucea, J., Jones, R.O.: Nucleus-driven crystallization of amorphous Ge2Sb2Te5: a density functional study. Phys. Rev. B 86(1–10), 144113 (2012)CrossRefGoogle Scholar
  30. 30.
    Soler, J.M., Artacho, E., Gale, J.D., Garca, A., Junquera, J., Ordejon, P., Sanchez-Portal, D.: The SIESTA method for ab initio order-N materials simulation. J. Phys. Condens. Matter 14, 2745–2779 (2002) Google Scholar
  31. 31.
    Anantram, M.P., Lundstrom, M.S., Nikonov, D.E.: Modeling of nanoscale devices. Proc. IEEE 96, 1511–1550 (2008)CrossRefGoogle Scholar
  32. 32.
    Svizhenko, A., Anantram, M.P., Govindan, T.R., Biegel, B., Venugopal, R.: Two-dimensional quantum mechanical modeling of nanotransistors. J. Appl. Phys. 91, 2343–2354 (2002)CrossRefGoogle Scholar
  33. 33.
    Lopez Sancho, M.P., Lopez Sancho, J.M., Rubio, J.: Highly convergent schemes for the calculation of bulk and surface Green functions. J. Phys. F Metal Phys. 15, 851 (1985)CrossRefGoogle Scholar
  34. 34.
    Koswatta, S.O., Hasan, S., Lundstrom, M.S., Anantram, M.P., Nikonov, D.E.: Nonequilibrium green’s function treatment of phonon scattering in carbon-nanotube transistors. IEEE Trans. Electron Devices 54, 2339–2351 (2007)CrossRefGoogle Scholar
  35. 35.
    Forst, M., Dekorsy, T., Trappe, C., Laurenzis, M., Kurz, H., Bechevet, B.: Phase change in Ge2Sb2Te5 films investigated by coherent phonon spectroscopy. Appl. Phys. Lett. 77, 1964–1966 (2000)CrossRefGoogle Scholar
  36. 36.
    Bahl, S.K.: Amorphous versus crystalline GeTe films III electrical properties and band structure. Appl. Phys. 41, 2196–2212 (1970)CrossRefGoogle Scholar
  37. 37.
    Liu, J.: Multiscale simulation of phase change memory. PhD thesis, University of Washington, Seattle, WA, USAGoogle Scholar
  38. 38.
    Yu, D., Brittman, S., Lee, J.S., Falk, A.L., Park, H.: Minimum voltage for threshold switching in nanoscale phase-change memory. Nano Lett. 8, 3429–3433 (2008)CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Department of Electrical EngineeringUniversity of WashingtonSeattleUSA

Personalised recommendations