Electrical switching properties and structural characteristics of GeSe–GeTe films

Abstract

Germanium chalcogenides, especially GeSe and GeTe alloys, have recently gained popularity because of their Ovonic threshold (volatile) and memory (non-volatile) switching properties, with great potential for electric storage applications. Materials designed in a pseudo-binary way may possess superior properties in their phase transition, e.g. GeTe–Sb₂Te₃ materials, and bring about revolutionary advances in optical storage. However, to date, the electrical switching behaviors of films of pseudo-binary GeSe–GeTe have not yet been studied, and neither have the structural characteristics. Herein, we present both the thermally and electrically induced switching behaviors of GeSe–GeTe film, as well as the structural evolution due to composition tuning. The crystallization temperature of GeSe–GeTe films increases with GeSe content quite sensitively. An atom-resolved picture of the GeSe–GeTe alloy with a state-of-the-art atomic mapping technology has been presented, where a randomly mixed arrangement of Se and Te atoms is determined unambiguously in Ge₅₀Se₁₃Te₃₄ with a GeTe-like rhombohedral structure. The local structural motifs in GeSe–GeTe, more specifically, sixfold coordinated octahedra with a distinguished degree of Peierls distortion and geometric variety, are essential to understand its electric properties. GeSe–GeTe alloy, Ge₅₀Se₁₃Te₃₄, based memory cells have been fabricated, showing a fast memory switching behavior and excellent retention of 10 years at 208 °C.