Low-Power and High-Speed Ag2S-Based Threshold Switching Device Enabled by Local Phase Transition-Assisted Filamentary Switching

Abstract

As the demand for low-power electronic devices in the Internet of Things (IoT) and embedded systems continues to grow, there is an increasing need for new devices that can operate at low voltages with minimal leakage current while maintaining fast switching speeds. To address this challenge, we developed a two-terminal threshold switching (TS) device based on Ag2S, demonstrating both low leakage current and fast switching speed at low voltages. The Ag2S-based TS devices were integrated in series with MOSFETs to form a 1T-1S array, designed for steep-slope FET applications. The Ag2S-based TS device exhibited a low leakage current of 2 pA, and when integrated with the MOSFET, the combined FET demonstrated a subthreshold swing (SS) of 3 mV/dec. Remarkably, the device exhibited a fast switching speed of 1 ns at 2.0 V. In addition, as the Ag2S composition approached stoichiometry, both leakage current and threshold voltage decreased, alleviating the voltage–time dilemma typically encountered in filamentary switching devices. These enhanced properties are attributed to the local phase transition of Ag2S and superionic conductivity of $\beta $ -Ag2S, which facilitate rapid ion transport and filament formation under an electric field. Furthermore, at a compliance current of $30~\mu $ A, the device demonstrated a turn-off speed of tens of nanoseconds. By increasing the compliance current to several hundred microamperes, the device also exhibited a short-term retention of several minutes, showing potential for application in next-generation DRAM-like volatile memory.