Abstract
Phase-change memory (PCM), a non-volatile memory technology, is considered the most promising candidate for storage class memory and neuro-inspired devices. It is generally fabricated based on GeTe–Sb2Te3 pseudo-binary alloys. However, natively, it has technical limitations, such as noise and drift in electrical resistance and high current in operation for real-world device applications. Recently, heterogeneously structured PCMs (HET-PCMs), where phase-change materials are hetero-assembled with functional (barrier) materials in a memory cell, have shown a dramatic enhancement in device performance by reducing such inherent limitations. In this Perspective, we introduce recent developments in HET-PCMs and relevant mechanisms of operation in comparison with those of conventional alloy-type PCMs. We also highlight corresponding device enhancements, particularly their thermal stability, endurance, RESET current density, SET speed, and resistance drift. Last, we provide an outlook on promising research directions for HET-PCMs including PCM-based neuromorphic computing.
Highlights
The emergence of data-driven technologies demands ultrahigh density and fast-access memories
We provide an outlook on promising research directions for HET-Phase-change memory (PCM) including PCM-based neuromorphic computing
Phase-change memory (PCM), which is a random-access memory based on phase-change chalcogenides, has emerged as a leading non-volatile Storage class memory (SCM) candidate, largely owing to its relatively good scalability, fast operating speed, and multi-level storage ability.[2,3]
Summary
The emergence of data-driven technologies demands ultrahigh density and fast-access memories. Conventional alloybased PCMs suffer from inhomogeneity in their phase and chemical compositions, both spatially and temporally, upon repetitive cycling This leads to large fluctuations in the electrical resistance of both the SET and RESET states. An interlayer functioning as a thermal barrier can be inserted between the PCM and bottom electrode to effectively localize heating by blocking heat dissipation.[15] This particular type of heterostructured PCM exhibits the desired low operation energy while unexpectedly improving stability-related properties Another major class of HET-PCMs is based on superlattice-like (SLL) heterostructures; one example is interfacial PCM (iPCM), first proposed by the Tominaga group in 2011.16 It showed excellent switching responsiveness and consumed substantially less energy during the SET process, possibly due to the confined local atomic switching of Ge atoms. Our perspective on the further optimization required for HET-PCM-based devices and their potential application in neuromorphics is provided
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