Inherent electron and hole trapping in amorphous phase-change memory materials: Ge₂Sb₂Te₅

Journal article

While the amorphous state of a chalcogenide phase-change material is formed inside an electronic-memory device via Joule heating, caused by an applied voltage pulse, it is in the presence of excess field-induced electrons and holes. Here, hybrid density-functional-theory calculations for glassy Ge2Sb2Te5 demonstrate that extra electrons are trapped spontaneously, creating deep traps in the band gap. Hole self-trapping is also energetically favourable, producing states around midgap. The traps have a relatively low ionization energy, indicating that they can easily be thermally released. Near-linear triatomic Te-Ge/Sb-Te/Ge/Sb environments are the structural motifs where the extra electrons/holes are trapped inside the glass network, highlighting that the intrinsic axial bonds of octahedral-like sites in amorphous Ge2Sb2Te5 can serve as charge-trapping centres. Trapping of two electrons in a chain-like structure of connected triads results in breaking of some of these highly polarizable long bonds. These results establish the foundations of the origin of charge trapping in amorphous phase-change materials, and they may have important implications for our understanding of resistance drift in electronic-memory devices and of electronic-excitation-induced athermal melting.publishedVersionPeer reviewe

Authors: Konstantinou, K; Elliott, SR; Akola, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Royal Society of Chemistry
• Journal: Journal of Materials Chemistry C Materials for optical and electronic devices
• Volume: 10
• Issue: 17
• Pages: 6744-6753
• Publication date: 2022-05-05
• DOI: 10.1039/d2tc00486k
• EISSN: 2050-7534
• ISSN: 2050-7526
• Language: English
• Keywords: Phase (matter); Optoelectronics; Electron; Molecular physics; Band gap; Octahedron; Atomic physics; Charge (physics); Amorphous solid; Crystallography; Trapping; Crystal structure; Materials science; Physics; Condensed matter physics