Ultralow-Power Circuit\nand Sensing Applications Based\non Subthermionic Threshold Switching Transistors

The most recent breakthrough in state-of-the-art electronics\nand\noptoelectronics involves the adoption of steep-slope field-effect\ntransistors (FETs), promoting sub-60 mV/dec subthreshold swing (SS)\nat ambient temperature, effectively overcoming “Boltzmann limit”\nto minimize power consumption. Here, a series integration of nanoscale\ncopper-based resistive-filamentary threshold switch (TS) with the\nIGZO channel-based FET is used to develop a TS-FET, in which the turn-on\ncharacteristics exhibit an abrupt transition over five decades, with\nan extremely low SS of 7 mV/dec, a high on/off ratio (>10<sup>9</sup>), and ultralow leakage current (40-fold decrease), ensuring excellent\nrepeatability and device yield. Unlike previous device-centric studies,\nthis work highlights potential circuit applications (logic-inverter,\npulse-sensor amplification, and photodetector) based on TS-FET. The\nsharp transition behavior of TS-FET enables the establishment of logic\ninverters with a high voltage gain of ≈800, with a circuit-level\ndemonstration achieving a bias-independent record-high intrinsic gain\n(>1000). A wearable pulse sensor integrated with an amplifier circuit\nensured the precise amplification of electrophysical signals by 450\ntimes. In addition, the application of a TS-FET-based photodetector\nfeatures high responsivity (1.08 × 10<sup>4</sup> mA/W) and detectivity\n(1.03 × 10<sup>20</sup> Jones). The low-power strategy of TS-FETs\nis promising for the development of energy-efficient integrated circuits\nalongside sensor-interconnected biomedical applications in wearable\ntechnology.