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

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.