Off-Delay Behavior of GeTe 9 OTS Selectors for High-Speed Memory Applications

Ovonic threshold switches (OTS) are widely used as selectors in cross-point arrays of resistive NVMs, where continuous word-line addressing demands high speed and strict disturbance immunity. For safe operation, the OTS must recover from the conductive state before the next word-line pulse, governed by the off-delay time rather than the intrinsic turn-off speed. Conventional methods fail to capture this off-delay behavior under realistic pulsed operation. In this letter, we propose a three-segment pulse scheme to directly quantify the off-delay of GeTe9OTS selectors. We find that the intrinsic turn-off speed has a narrow distribution (~10 ns), while the off-delay is more broadly distributed (79–173 ns). By tuning the write-pulse amplitude, width, series resistance, and temperature, we identify the ON-state current as the primary factor controlling the off-delay, with elevated temperature and self-heating accelerating the relaxation of the conductive defect cluster. The off-delay behavior is explained by thermally assisted shrinkage of the defect cluster, providing a physical basis for design guidelines on the minimum word-line recovery time trecin high-speed resistive-NVM crossbar arrays.