In this study, we investigate the electrical characteristics of a W/Si–Te–As–Ge/W ovonic threshold switch (OTS) under various conditions to reveal the origin of its forming and its effect on the subsequent threshold switching. Our results indicate that the forming of the OTS is a process of generating a metastable filamentary conductive path with a statistical nature, which leaves behind the lowest energy level of the activated trap, thereby significantly affecting the subsequent conduction as well as the dynamics of the threshold switching in the OTS. In addition, we apply a hot forming technique to control the distribution and energy level of the residual traps. By forming at elevated temperatures, the overshoot damage due to abrupt switching can be reduced. As a result, the trap distance and activation energy can be increased, the off current decreases from 54 to 7 nA (1/2 Vth read), and the threshold voltage increases from 1.5 to 1.7 V.
This study investigated the impact of a Ge2Sb2Te5 (GST) thermal barrier on the performance of NbO2-based selector devices. Our findings showed that the GST barrier could significantly decrease the off-state leakage current from 3 μA to 300 nA without increasing the threshold switching voltage owing to its insulation properties and high thermal resistance. We also found that the GST barrier can effectively contain the Joule heat within the NbO2 switching region, as confirmed through a cryogenic analysis of the thermal resistance of GST. The results showed that the GST/NbO2 device had a thermal resistance 3.48 times higher than that of a single-layer NbO2 device. Our results provide design guidelines for utilizing a barrier layer to reduce the leakage current in low-power threshold switching devices.
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