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.
Thermal conduction strongly influences the programming
energy and speed in phase-change-memory devices.
The thermal conductivity of the crystalline phase of Ge2Sb2Te5
can be strongly anisotropic due to phase impurities at grain
boundaries. This letter models this effect using effective medium
arguments, lends further support to the hypothesis that phase
impurities are responsible for the anisotropy, and estimates the
impact of anisotropic heat conduction on device performance.
Electrothermal simulations predict that the reduced in-plane conductivity
will allow closer spacing of lateral-cell devices and reduce
the reset programming current by 20%–30%.