Heterogeneously structured phase-change materials and memory

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.

Projected Mushroom Type Phase‐Change Memory

“…Important device nonidealities from the intrinsic material physics of phase-change materials [12][13][14][15][16][17][18] thus arise and reduce the numerical precision achievable with this technology. Both materials and device engineering have been proposed as solutions [19][20][21][22][23] to minimizing these non-idealities. Device engineering invokes novel cell architectures, including the concept of projected PCM.…”

Enabling Active Nanotechnologies by Phase Transition: From Electronics, Photonics to Thermotics

“…Therefore, most research in this area focuses on reducing RESET power and improving thermal stability. In a memory cell, data retention temperature for 10 years ( T 10years ) is a significant parameter to evaluate the thermal ability, which can be defined by the Arrhenius equation where t is the failure time for the initial resistance to drop to its half value, τ is a proportional time constant, E a is the activation energy for crystallization, and k B is the Boltzmann constant.…”

“…Additionally, other characteristics of phase transition-based memory such as resistance drift were also improved by incorporating with impurities. , The resistance drift in SET states originates from the stress release after quick quenching in the RESET process, which causes the material relaxation to lower energy state. Basically, the resistance drift is governed by a power-law relationship as ,, Here t is the time since the cell is programmed, and R ( t 0 ) is the resistance at time t 0 . The power term ν is the drift coefficient which can evaluate the resistance drift.…”

“…Apart from material modification, new designs of memory cells have also been demonstrated to reduce power consumption. As the RESET current is proportional to BEC area, one strategy is to minimize the contact size by optimizing architectural design such as edge contact type, confined volume type, − μ-trench type, , ring type. , The schematic diagrams of these cell designs are shown in Figure .…”

“…In Figure , we have summarized the excitation, phase transition, and typical applications of TMOs and chalcogenides in electrical nanodevices, nanophotonics, and thermal radiation control. In last few decades, there are various literature reviews on recent advances of PCMs in nanophotonics, , metasurfaces, ,, nonvolatile memory, ,− and neuromorphic devices. , However, a comprehensive introduction from material physics and chemistry (particularly on emerging TMOs and chalcogenides) to their applications in nanodevices (including electronics, nanophotonics, and thermotics) is still lacking. In this review, we start by introducing the physics and mechanism of transition oxide and chalcogenide PCMs.…”