Characterization and Performance Analysis of Reduced Graphene Oxide ISFET Sensors Using TCAD and MATLAB

In this work, we propose a novel ion-sensitive field-effect transistors (ISFET) architecture in which reduced graphene oxide (rGO) serves a dual function as both the pH-sensitive membrane and the conductive channel within an electrolyte/rGO/SiO ₂ /Si configuration, referred to as an rGO-ISFET. Using the site-binding model, we simulate the surface charge density ( σ ₀) at the electrolyte/rGO interface to analyze the sensor behavior over a wide pH range. Both n-type (NrGO) and p-type (PrGO) structures are examined. Simulations performed using ATLAS in combination with MATLAB include transfer and output characteristics. For both NrGO and PrGO devices, the gm/IDS ratio reaches 33.5 V ⁻¹ , while the slope |gm/pH| is 0.745 μS pH ⁻¹ . The normalized slope (Sgm) depends on the rGO doping type, varying from +17.82 %·pH ⁻¹ at pH 2 to +7.09 %·pH ⁻¹ at pH 12 for NrGO, and from −7.09 %·pH ⁻¹ at pH 2 to −17.82 %·pH ⁻¹ at pH 12 for PrGO. At pH 7, a three-dimensional analysis of cut-off frequency (fc), gain-bandwidth product (GBW), and response time ( τ ) as functions of transconductance (gm) and gate-to-source voltage (VGS) shows a significant performance enhancement of the proposed rGO-ISFET. fc reaches =31.79 MHz, GBW = 8.7 MHz, and τ =10 ns.