Chalcogenide materials engineering for phase-change memory and future electronics applications. From Sb-Te to Bi-Te

Chalcogenide materials play essential roles in modern nonvolatile memory technology in the form of both phase-change memory (PCM) and selector devices. Herein, Bi-Te binary alloys are explored as an alternative candidate for superlattice (SL) or interfacial PCM (iPCM). GeTe/Bi${}_4$Te${}_3$ (GT/BT) SL exhibits similar structural features to conventional GeTe/Sb${}_2$Te${}_3$ (GT/ST) SL, such as highly oriented crystal grains and intermixing. Furthermore, preliminary device measurements show that Ge-Bi-Te (GBT) SL switches in a similar manner to conventional Ge-Sb-Te (GST), suggesting that they may be a promising candidate for memory applications. In addition, Bi${}_2$Te${}_3$/Sb${}_2$Te${}_3$ (BT/ST) heterostructure films have been successfully fabricated and show clear interface stacking at the atomic level. Although the BT/ST heterostructure is ostensibly a p-n junction, rectifying behavior is not observed in current (I)-voltage (V) measurements due to the existence of a large number of carriers in both layers. Finally, density functional theory (DFT)-based simulations suggest that an ideal BT/ST heterostructure may possess intriguing topological properties that can enable novel functional devices. The Bi-Te binary alloys offer promising potential for optimizing PCM performance as well as for the realization of novel functional electronic devices. (© 2020 Wiley‐VCH GmbH)