Overcoming the Thermal Stability Limit of Chalcogenide Phase‐Change Materials for High‐Temperature Applications in GeSe_1−<i>x</i>Te_<i>x</i> Thin Films

Abstract

The electrical, optical, and structural properties of GeSe 1− x Te x phase‐change materials thin films with 0.16 ≤ x ≤1 prepared by cosputtering of GeSe and GeTe targets are studied. The crystallization temperature of the films increases significantly when the Te content decreases. Se‐rich films show an extremely large electrical contrast between their amorphous and crystalline states. A high polarizability of the crystalline phase is observed in the entire x range and is related to the presence of metavalent bonds. This is explained by the persistence of a rhombohedral crystalline phase, isostructural to GeTe, in the GeSe 1− x Te x films down to x = 0.16. Hence, the substitution of only 16 at% of the Se atoms by Te atoms transforms the covalent GeSe into a phase‐change material with a huge and unprecedented contrast of resistivity (up to 11 orders of magnitude) and a very high thermal stability (up to 10 years at 272 °C) for an alloy exhibiting no phase separation upon crystallization. This outstanding combination of properties makes Se‐rich GeSe 1− x Te x thin films extremely promising for integration in memory devices requiring a very high data retention such as automotive and embedded applications.