Nanosecond-scale transient defect spectroscopy of switching and relaxation dynamics in GeAsSe Ovonic Threshold Switching Devices

Abstract

Ovonic Threshold Switch (OTS) devices are crucial non-linear selectors in high-density memory arrays, suppressing sneak-path leakage. Defects critically influence their switching behaviour, speed, and reliability. Despite decades of study, the transient defect dynamics of OTS, particularly under fast electrical stimuli, remain poorly understood. In this work, we present a nanosecond-scale transient defect spectroscopy study of GeAsSe OTS devices, revealing a two-stage switching process governed by two distinct sets of defect characteristics. Group D1 defects delocalize initiating 1st stage of fast switch-on (<0.4ns) at high electric field but localize slower in 2nd stage of switch-off and relaxation (>μs). Group D2 defects delocalize in 2nd stage of switch-on at lower fields and higher on-state currents but rapidly localize and relax (~ns) in 1st stage of switch-off and relaxation. Impact of operation conditions on two sets of defect dynamics in switch-on/-off and relaxation is experimentally demonstrated. These findings provide crucial temporal insights and quantitative validation of prior OTS transient switching models, offering valuable guidance for designing high-speed OTS selectors.