  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 a 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 ~4X reduction of the effective cross-plane thermal conductivity of
the SL stack (as-deposited polycrystalline) compared to 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 (~2000X) between
the in-plane and cross-plane directions due to the weakly interacting van der
Waals gaps. This work uncovers electro-thermal transport in SLs based on Sb2Te3
and GeTe, for improved design of low-power PCM.
