Extreme Bond Ionicity in Mg─Te Chalcogenides for Ultrathin Low Voltage Selector‐Only Memory beyond the Leakage Scaling Limit

Conventional ovonic threshold switching (OTS) chalcogenides face a fundamental scaling limit for selector‐only memory (SOM), because aggressive thickness scaling increases leakage current and hinders reliable low voltage operation. Here, this trade‐off can be overcome by exploiting the unique materials characteristics of the Mg─Te chalcogenide system. Guided by the bonding ionicity map and supported by density functional theory calculations, Mg─Te is identified as an optimal telluride material whose highly ionic bonding is associated with deeper trap levels, a large memory window of 1.75 V, and suppressed leakage in 20 nm devices. Structural analyses and multiscale simulations suggest that the spontaneous phase separation in Mg 1 Te 3 forms MgTe‐like ordered nanodomains and Te‐rich amorphous regions, providing structural partitioning that may constrain the effective amorphous switching network and reduce stochastic switching variability. With a thin Hf interlayer, the 5 nm Mg 1 Te 3 device achieves narrow SET/RESET switching uniformity of σ = 15/28 mV at ± 2.5 V operating voltage, representative 10 ns programming speed, and write endurance exceeding 10 10 cycles in the best‐performing device. These results highlight Mg─Te as a promising basis for highly scaled ultralow voltage SOM through the combined roles of ionic bonding, structural partitioning, and interfacial engineering.