Modulation of GeSe and As2Se3 motifs to optimise GeAsSe OTS performance and its mechanism

Abstract

Ovonic threshold switching (OTS) selectors are pivotal in the construction of highly integrated 3D crosspoint array volatile storage systems, necessitating materials with superior electrical properties. GeAsSe emerges as a prominent contender for OTS materials, delivering exceptional performance metrics. However, the precise elemental ratio optimization and the mechanisms behind its performance have not been thoroughly elucidated. Therefore, this study explores the optimization of GeAsSe materials through meticulous ratio modulation of GeSe and As₂Se₃ precursors, targeting high thermal stability, low leakage currents, and robust endurance. We found that the ideal ratio of Ge(As)–Se–Se to Ge–As bonds is formed when the mean covalent number of materials is close to 2.5, thereby effectively enhancing the stability of materials. This results in a reduction in the leakage current of approximately one order of magnitude, as well as enhanced operational speed and endurance, ultimately enabling a back-end-of-line-compatible OTS selector with ∼2 nA leakage current, ∼10 ns speed and >10⁹ cycles endurance after annealing at 400 °C for 30 minutes. Our research presents a thorough elucidation of the mechanisms underpinning the exceptional performance of GeAsSe materials in OTS applications, providing critical insights that are expected to propel future developments in OTS material systems.