Elemental electrical switch enabling phase segregation-free operation

• Published in: Science (American Association for the Advancement of Science) 2021-12, Vol.374 (6573), p.1390-1394
• Main Authors: Shen, Jiabin, Jia, Shujing, Shi, Nannan, Ge, Qingqin, Gotoh, Tamihiro, Lv, Shilong, Liu, Qi, Dronskowski, Richard, Elliott, Stephen R, Song, Zhitang, Zhu, Min
• Format: Article
• Language: English
• Subjects: Chalcogenides; Chips (memory devices); Commercialization; Competitive materials; Computer memory; Memory; Nonlinear response; Phase change materials; Phase transitions; Switches; Switching; Tellurium; Threshold voltage; Voltage
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.abi6332

Nonvolatile phase-change memory has been successfully commercialized, but further density scaling below 10 nanometers requires compositionally and structurally homogeneous materials for both the memory cell and the associated vertically stacked two-terminal access switch. The selector switches are mostly amorphous-chalcogenide Ovonic threshold switches (OTSs), operating with a nonlinear current response above a threshold voltage in the amorphous state. However, they currently suffer from the chemical complexity introduced by the quaternary or even more diverse chalcogenide compositions used. We present a single-element tellurium (Te) volatile switch with a large (≥11 megaamperes per square centimeter) drive current density, ~10 ON/OFF current ratio, and faster than 20 nanosecond switching speed. The low OFF current arises from the existence of a ~0.95–electron volt Schottky barrier at the Te–electrode interface, whereas a transient, voltage pulse–induced crystal-liquid melting transition of the pure Te leads to a high ON current. Our discovery of a single-element electrical switch may help realize denser memory chips.