An ovonic threshold switch selector with ultralow threshold voltage drift coefficient for cross-point memory applications

Abstract

Ovonic threshold switch (OTS) selectors, based on chalcogenides, are indispensable components for suppressing sneak currents of high-density 3D cross-point memory chips. The threshold voltage drift characteristic of OTS selectors is a major concern since it impacts the read window margin. Based on this, we conducted the first investigation of a new type of OTS material, In₅Te₉As₃₀Se₅₆, and it exhibits an ultralow drift coefficient of ∼0 mV dec⁻¹, a leakage current of 1 nA, a speed of ∼10 ns, a lifetime over 10⁸ cycles, and an ON-current density of >26 MA cm⁻². The drift-free threshold voltage arises from strong In–Se bonds and the absence of additional deep defect state distributions in the film. In contrast, other In–Te–As–Se components exhibit drift behavior due to the formation of thermodynamically unstable deep defect states from distorted tetrahedral As-centered atomic clusters, which are prone to structural relaxation. These findings offer valuable insights into the mechanisms behind the threshold voltage drift in OTS materials, which could aid in designing superior selectors in the future.