Binary Ge−Te Chalcogenide as a Toxic-Element-Free Platform for Polarity-Dependent Selector-Only Memory via Composition Engineering

The growing demand for high-density and energy-efficient memory has motivated the development of selector-only memory (SOM) as a simplified alternative to conventional one-selector−one-resistor architectures. However, most reported SOM devices rely on multicomponent chalcogenides, buffer layers, or toxic elements, which complicate fabrication and limit scalability. Here, SOM operation is demonstrated in a simple binary Ge−Te system without buffer layers, interfacial engineering, or toxic elements. By systematically tuning the stoichiometry, a well-defined composition window is identified where pronounced SOM behavior emerges, exhibiting a polarity-dependent threshold-voltage shift of up to ∼1.5 V. Pulse-based electrical measurements reveal a composition-dependent trade-off between memory window characteristics and reliability metrics, including endurance exceeding 3 × 10 8 stress pulses and data retention on the order of 10 8 s in optimized composition. To elucidate the physical origin of the SOM behavior, comprehensive analyses combining trap-assisted hopping modeling with transmission electron microscopy and X-ray photoelectron spectroscopy were performed. These analyses indicate that polarity-driven modifications of local bonding configurations and defect energetics within the amorphous Ge−Te layer lead to asymmetric trap transport pathways and history-dependent threshold voltages. Thus, this work highlights binary Ge−Te as a minimal and toxic-element-free SOM material platform, providing insights for next-generation memory technologies.