Effective threshold voltage modulation technique for steep-slope 2D atomic threshold switching field-effect transistor

Two-dimensional (2D) atomic threshold switching field-effect transistors (ATS-FETs), which integrate 2D FET with threshold switching (TS) devices, have garnered attention as part of the subthreshold swing (SS) improvement for next-generation low-power devices. For industrial applications of 2D ATS-FET, it is important to secure the threshold voltage (V_th) modulation technique. Here, V_th engineering is performed by altering the counter electrode (CE) of a TS device, and the electrical performance of the ATS-FET is systematically investigated. The work function difference between the active electrode and CE alters the internal electric field (E-field) formed between these two electrodes. This severely affects the metal ion migration of the active electrode and induces the V_th shift of the ATS-FET. Because the proposed V_th adjusting technique does not affect the channel material, the MoS₂ ATS-FET with the proposed technique can shift V_th while maintaining a high on–off ratio of >10⁵ A on average and achieves an ultra-low average SS of ∼10.929 mV/dec. Moreover, the SS variation due to the random interface traps between the channel and gate dielectric is sufficiently suppressed. This study is expected to be a cornerstone for ATS-FET research by offering a compact platform to adjust V_th without deteriorating steep-slope characteristics.