Reduction of thermal conductivity in Y_xSb_(2-) _xTe_3 for phase change memory

摘要

Thermal conductivity (κ) is one of the fundamental properties of materials for phase change memory (PCM) application, as the set/reset processes strongly depend upon heat dissipation and transport. The κ of phase change materials in both amorphous and crystalline phases should be quite small, because it determines how energy-efficient the PCM device is during programming. At a high temperature, the electronic thermal conductivity (κ_e) is always notable for semiconductors, which is still lacking for antimony telluride under doping in the literature as far as we know. In this paper, using density functional theory and Boltzmann transport equations, we report calculations of lattice thermal conductivity κ_L and electronic thermal conductivity κ_e of the yttrium doped antimony telluride. We show that the average value of thermal conductivity decreases from ∼2.5 W m~(-1)K~(-1) for Sb_2Te_3 to ∼1.5 W m~(-1)K~(-1) for Y_(0.167)Sb_(1.833)Te_3. This can be attributed to the reduced κ_L and κ_e, especially the κ_e at high temperature (near melting point). We further point out that the increased effective mass of carriers and the flat valance band edge are responsible for the decrease of κ_e. The reduced thermal conductivity is highly desirable for the decrease of heat dissipation and transport in PCM operations, which can increase the density of memory and reduce energy consumption.