An Ion-Sensitive Floating Gate FET Model: Operating Principles and Electrofluidic Gating

Abstract

We present a model that can be used to compute the charging and potential at any point of the electrochemical system comprising the ion-sensitive floating gate FET (ISFGFET) exposed to an electrolyte solution. In contrast to ion-sensitive FETs, the sensor has an additional control input gate. The model predicts the possibility for electrofluidic gating when the control gate (CG) is used in conjunction with a reference electrode (RE). Electrofluidic gating is the field-effect control over the electric double layer. We consider the applicability of electrofluidic gating in realizable devices and simulate the relationships between oxide properties and electrolyte solution to varying potentials of the CG and the RE. The oxide/electrolyte solution model is merged to the SPICE model of the transistor to create a unified model that can be used to simulate the transfer characteristics of the sensor in absolute terms to change input and electrolyte solution conditions. We simulate the sensor transfer characteristics with common Al 2 O 3 surface to change the pH of the electrolyte solution and compare them to measurements. The results clarify the operation of ISFGFET and its applicability in electrofluidic gating.

A numerical simulation tool for nanoscale ion‐sensitive field‐effect transistor

“…For the purpose of behavioral benchmarking, we first compared the results of the developed simulation tool with measured results taken from [10]. The measured values were extracted by a digitizing software.…”

“…Àlog 10 [H + ] s 1 1 maximum value at the end of the pH range for both experimental and simulation results. The results are shown in Figure 4, where the simulated relative drain current I D (relative to its maximum value) is plotted for an ISFET with Al 2 O 3 insulator of thickness 6 nm and compared to the measured relative values found in [10] for three pH values: 4, 7, and 10. Although the threshold voltage in simulation results and measured results are different, the shift in this threshold voltage because of pH is the same (58.3 mV/ pH) in both cases.…”

“…Using the first concept of sensitivity given by S 1 in (12), the variation of the drain current versus pH value is depicted in Figure 5 [10]. For the sake of clarity, current in both cases is divided by its maximum value and plotted in relative units.…”

“…Research work on ISFET has been made through various approaches including experimental characterization [7,8], modeling [9][10][11][12], and software simulation [2,3,8]. Regarding software simulation approach, it is usually based on using technology computer-aided design (TCAD) software of conventional MOSFETs, then, introducing some modifications to conform to ISFET operation [2,3].…”

Influence of Bioreceptor Layer Structure on Myelin Basic Protein Detection using Organic Field Effect Transistor‐Based Biosensors

“…Organic field‐effect transistor (OFET)‐based sensors are currently considered for various applications such as gas sensing, biosensing, and pressure sensing . OFET‐based biosensors are being widely studied for potentially fast clinical diagnostics, with the advantages of flexibility, sensitivity, and low cost . Particularly, OFET‐based biosensors for protein sensing have progressed remarkably for label‐free analyte detection based on the specific immune binding property innate to particular antibodies .…”