Uncovering Thermal and Electrical Properties of Sb₂Te₃/GeTe Superlattice Films

Superlattice-like phase change memory (SL-PCM) promises lower switching current than conventional PCM based on Ge₂Sb₂Te₅ (GST); however, a fundamental understanding of SL-PCM requires detailed characterization of the interfaces within such an SL. Here we explore the electrical and thermal transport of SLs with deposited Sb₂Te₃ and GeTe alternating layers of various thicknesses. We find up to an approximately four-fold reduction of the effective cross-plane thermal conductivity of the SL stack (as-deposited polycrystalline) compared with polycrystalline GST (as-deposited amorphous and later annealed) due to the thermal interface resistances within the SL. Thermal measurements with varying periods of our SLs show a signature of phonon coherence with a transition from wave-like to particle-like phonon transport, further described by our modeling. Electrical resistivity measurements of such SLs reveal strong anisotropy (∼2000×) between the in-plane and cross-plane directions due to the weakly interacting van der Waals-like gaps. This work uncovers electrothermal transport in SLs based on Sb₂Te₃ and GeTe for the improved design of low-power PCM.