Modeling responses to heterogeneous adsorption in graphene FET biosensors via circuit simulation

Graphene field-effect transistors (GFETs) have emerged as highly promising platforms for biosensing applications owing to their exceptional sensitivity and capability for label-free detection. However, interpreting their transfer characteristics remains challenging, primarily because of complex signal variations induced by spatially heterogeneous biomolecular adsorption. In this study, we modeled the heterogeneous graphene channel as a resistor grid network to examine how local modulation of carrier density influences the electrical behavior of GFETs. Our simulations replicated the nonlinear and non-monotonic variations observed in RDS–VGS curves characteristics following biomolecular adsorption. Notably, the peak voltage shift (ΔVpeak) and resistance change (ΔRpeak) exhibited nontrivial dependencies on the adsorption ratio. These findings indicate that conventional metrics, such as the charge neutrality point, are inadequate for reliably quantifying adsorption levels under heterogeneous conditions. The proposed approach offers a fundamental framework for understanding signal variability in GFET-based biosensors and for guiding the development of more robust sensing strategies.