Low-Frequency Noise and Stability in Electrolyte-Gated Nanoscale Silicon Field-Effect Transistor Sensors

Electrolyte-gated nanoscale silicon field-effect transistors (Si FETs), including silicon nanoribbon FETs (SiNRFETs) and nanowire FETs (SiNWFETs), have emerged as highly promising platforms for chemical and biological sensing. As these sensors move from proof-of-concept demonstrations toward quantitative assays, practical performance is increasingly governed not only by nominal sensitivity, but also by their signal-to-noise ratio (SNR) and baseline stability. Low-frequency noise (LFN), typically arising from carrier-number and mobility fluctuations in the solid-state device, as well as reversible ion adsorption/desorption processes at the solid-liquid interfaces, is generally characterized by an approximately 1/f-dependent power spectral density. It limits the minimum resolvable signal and thus determines the limit-of-detection (LoD). In parallel, slower nonstationary processes, including ion penetration and reference-electrode drift, cause baseline instability that complicates quantitative sensing and array calibration. This review discusses LFN and instability in electrolyte-gated nanoscale Si FET sensors as a coupled device-interface-readout problem. Mitigation strategies are also summarized. Representative examples illustrate how dominant noise sources can be identified and suppressed. Finally, we highlight the applications of low-noise and low-drift FET sensors. Next-generation electrolyte-gated nanoscale Si FET sensors require codesign of the transducer, sensing interface, electrolyte/reference environment, and front-end electronics to achieve a low LoD and high detection accuracy.