Ultralow-Power Circuit and Sensing Applications Based on Subthermionic Threshold Switching Transistors

The most recent breakthrough in state-of-the-art electronics and optoelectronics involves the adoption of steep-slope field-effect transistors (FETs), promoting sub-60 mV/dec subthreshold swing (SS) at ambient temperature, effectively overcoming "Boltzmann limit" to minimize power consumption. Here, a series integration of nanoscale copper-based resistive-filamentary threshold switch (TS) with the IGZO channel-based FET is used to develop a TS-FET, in which the turn-on characteristics exhibit an abrupt transition over five decades, with an extremely low SS of 7 mV/dec, a high on/off ratio (>10⁹), and ultralow leakage current (40-fold decrease), ensuring excellent repeatability and device yield. Unlike previous device-centric studies, this work highlights potential circuit applications (logic-inverter, pulse-sensor amplification, and photodetector) based on TS-FET. The sharp transition behavior of TS-FET enables the establishment of logic inverters with a high voltage gain of ≈800, with a circuit-level demonstration achieving a bias-independent record-high intrinsic gain (>1000). A wearable pulse sensor integrated with an amplifier circuit ensured the precise amplification of electrophysical signals by 450 times. In addition, the application of a TS-FET-based photodetector features high responsivity (1.08 × 10⁴ mA/W) and detectivity (1.03 × 10²⁰ Jones). The low-power strategy of TS-FETs is promising for the development of energy-efficient integrated circuits alongside sensor-interconnected biomedical applications in wearable technology.