Arsenic-Free Selector-Only Memory with Deterministic Multibit Programming and Nondestructive Spike-Frequency Readout

Abstract

Selector-only memory (SOM) integrates signal selection and data storage within a single chalcogenide element through polarity-dependent threshold voltage (Vth) modulation, offering a compact route to high-density nonvolatile storage. However, its practical multilevel deployment has been hindered by three barriers: the toxicity of arsenic-containing glasses, stochastic Vth programming, and state-destructive readout. Here, we demonstrate deterministic multibit programming combined with a nondestructive spike-frequency readout in an arsenic-free Ge–Se–Te SOM. Rational blending of Se and Te anions stabilizes the amorphous network, affording a wide memory window (∼2.0 V) for multistate margins, together with low variability (5–6%), extended endurance (>106 cycles), and thermal stability up to 400 °C. Transient analysis of post-threshold voltage redistribution reveals that Vth placement is governed jointly by the internal electric field and programming current, rather than total power dissipation. Guided by this insight, we achieve reproducible 2-bit operation with ∼0.5 V interstate separation sustained over 500 cycles in both individual devices and a 128-cell array. Under subthreshold bias, capacitive charging produces current spikes whose frequency encodes the stored state (0.5–2.5 MHz), enabling robust readout with minimal Vth disturbance. These results establish nontoxic chalcogenide glasses with decoupled write and read protocols as a scalable design framework for reliable multibit SOM storage.