  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 Sb2Te3/GeTe alternating layers of various thicknesses. We find a ~3x
reduction of the effective cross-plane thermal conductivity of Sb2Te3/GeTe (4/1
nm/nm) SL compared to crystalline GST 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 Sb2Te3/GeTe SLs, for improved
design of low-power PCM.
