Electrical conduction in chalcogenide glasses of phase change memory

TLDR

Amorphous chalcogenides, used in optical storage and phase‑change memory, have been studied for decades, yet their non‑ohmic conduction mechanisms remain debated. This review consolidates current knowledge on dc conduction in these glasses, evaluates twelve field‑dependent transport mechanisms, and calls for further studies to discriminate among competing models. The authors review experimental data and the physics of localized states in chalcogenide glasses, then assess twelve mechanisms such as Poole‑Frenkel ionization, Schottky emission, hopping, field‑induced delocalization, space‑charge‑limited current, field emission, percolation band conduction, and crystalline‑inclusion transport. Most candidates provide more or less satisfactory fits to the observed non‑linear IV data.

Abstract

Amorphous chalcogenides have been extensively studied over the last half century due to their application in rewritable optical data storage and in non-volatile phase change memory devices. Yet, the nature of the observed non-ohmic conduction in these glasses is still under debate. In this review, we consolidate and expand the current state of knowledge related to dc conduction in these materials. An overview of the pertinent experimental data is followed by a review of the physics of localized states that are peculiar to chalcogenide glasses. We then describe and evaluate twelve relevant transport mechanisms with conductivities that depend exponentially on the electric field. The discussed mechanisms include various forms of Poole-Frenkel ionization, Schottky emission, hopping conduction, field-induced delocalization of tail states, space-charge-limited current, field emission, percolation band conduction, and transport through crystalline inclusions. Most of the candidates provide more or less satisfactory fits of the observed non-linear IV data. Our analysis calls upon additional studies that would enable one to discriminate between the various alternative models.