Indium turns tellurium into an ovonic threshold switching selector via a stabilizing amorphous network

Abstract

Selector devices that can alternate between metallic and insulating states are essential for the integration of cross-point memory as they effectively prevent current leakage. Recently, a pure tellurium (Te) selector relying on liquid-crystal transition has demonstrated outstanding potential, but high-performance memory chips tend to avoid the use of liquids. In our study, we demonstrate that incorporating only 10% indium (In) into Te can transform it into a high-performance ovonic threshold switching (OTS) selector—an effect observed exclusively in the amorphous phase of chalcogenide materials. Our InTe₉ device exhibits an exceptional cycling endurance of over 10⁸ cycles, an impressive on/off ratio close to 10⁴, and fast switching speeds below 10 nanoseconds. Ab initio molecular dynamic calculations uncovered that the introduction of In could significantly boost the thermal stability of the pristine Te phase. Furthermore, electronic structure calculations highlight the presence of mid-gap states, which are the fundamental cause of OTS behavior, originating from over-coordinated Te atoms within amorphous InTe₉ structures. Unlike amorphous Te, wherein all Te atoms adopt an octahedral-like arrangement, a small fraction of Te atoms tend to form distorted tetrahedral configurations in InTe₉, facilitating the formation of stable mid-gap states. These findings provide new avenues for the optimization of electrical switching materials and offer valuable insights into the fundamental physics governing OTS mechanisms.