Noise Spectroscopy Analysis of Ion Behavior in Liquid Gate‐All‐Around Silicon Nanowire Field‐Effect Transistor Biosensors

Abstract The transport and noise properties of fabricated, high‐performance, gate‐all‐around silicon liquid‐gated nanowire field‐effect transistor devices are investigated in different concentrations of MgCl₂ solutions. The critical concentration of MgCl₂ solution for charge inversion at the solid‐liquid interface is verified using noise spectroscopy and confirmed using the capacitance‐voltage measurement technique. In this study, it is found that the Hooge parameter (α_H) and the equivalent input noise (S_U) can effectively reflect the ion behavior on the surface of the nanowire. Moreover, the noise curves for α_H and S_U indicate two turning points at concentrations of 10⁻⁴ and 10⁻¹ m for a peak and a valley, respectively. The noise transformation is related to the behavior of ions near the solid‐liquid interface in solutions with different MgCl₂ concentrations is revealed. The results show that noise spectroscopy is a powerful method for monitoring charge dynamic processes in the research field of biosensors.