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

Abstract

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 Mg1Te3 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 Mg1Te3 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 1010 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.