Understanding Superlattices of Sb₂Te₃/Ge₄Sb₆Te₇ for Low-Power and High-Speed Phase Change Memory

Conventional data storage technologies are approaching fundamental limits, and one of the most promising alternatives is based on phase-change materials, typically chalcogenides that can reversibly switch between low- and high-resistance states. The success of such phase change memory (PCM) [1] depends on achieving simultaneously low-power and high-speed operation at nanometer-scale dimensions. Here we introduce a novel phase-change superlattice (SL) material with Sb₂Te₃ and Ge₄Sb₆Te₇ layers (2/2 nm thin), which enable electron and phonon confinement and scattering, leading to material properties tunable with the SL layer thicknesses. In PCM devices, this SL enables record-low switching power density (5 MW/cm²) and fast switching speed (40 ns). Nanoscale device dimensions and strong phonon confinement within the SL enable the energy-efficient phase change in our devices [2]. Unlike traditional PCM materials, GST467 contains epitaxial SbTe nanoclusters within the Ge-Sb-Te matrix [3], which act as precursors for crystallization, boosting the switching speed of GST467. These results provide fundamental insights and practical applications of superlattice PCM for energy-efficient data storage.

Refs: [1] R. Ranica et al., IEDM (2020). [2] A. I. Khan, E. Pop et al., EDL (2021). [3] A. I. Khan, E. Pop et al., Advanced Materials (2023).