Effects of stoichiometry on the transport properties of crystalline phase-change materials

Scientific Reports
W ZhangR Mazzarello

Abstract

It has recently been shown that a metal-insulator transition due to disorder occurs in the crystalline state of the GeSb2Te4 phase-change compound. The transition is triggered by the ordering of the vacancies upon thermal annealing. In this work, we investigate the localization properties of the electronic states in selected crystalline (GeTe)x-(Sb2Te3)y compounds with varying GeTe content by large-scale density functional theory simulations. In our models, we also include excess vacancies, which are needed to account for the large carrier concentrations determined experimentally. We show that the models containing a high concentration of stoichiometric vacancies possess states at the Fermi energy localized inside vacancy clusters, as occurs for GeSb2Te4. On the other hand, the GeTe-rich models display metallic behavior, which stems from two facts: a) the tail of localized states shrinks due to the low probability of having sizable vacancy clusters, b) the excess vacancies shift the Fermi energy to the region of extended states. Hence, a stoichiometry-controlled metal-insulator transition occurs. In addition, we show that the localization properties obtained by scalar-relativistic calculations with gradient-corrected functional...Continue Reading

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Citations

Jan 7, 2020·Journal of Physics. Condensed Matter : an Institute of Physics Journal·Young-Sun Song, Seung-Hoon Jhi
Apr 14, 2018·Scientific Reports·Jos E BoschkerRaffaella Calarco
Jul 7, 2020·ACS Nano·Munisa NurmamatAkio Kimura

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