[paper] Compact Modeling of pH-Sensitive FETs Based on 2D Semiconductors

Tarek El Grour, Francisco Pasadas, Alberto Medina-Rull, Montassar Najari, Enrique G. Marin, Alejandro Toral-Lopez, Francisco G. Ruiz, Andrés Godoy, David Jiménez and Lassaad El-Mir

Compact Modeling of pH-Sensitive FETs Based on Two-Dimensional Semiconductors

arXiv:2109.06585 [physics.app-ph; submitted on 14 Sep 2021]

DOI: 10.1109/TED.2021.3112407

   

LAPHYMNE Laboratory, Gabes University, Gabes, Tunisia

PEARL Laboratory, Departamento de Electrónica y Tecnología de Computadores, Universidad de Granada, Spain

The Innovation and Entrepreneurship Centre, Jazan University, Jazan, Saudi Arabia.

Departament d’Enginyeria Electrònica, Escola d’Enginyeria, Universitat Autònoma de Barcelona, Spain

Abstract: We present a physics-based circuit-compatible model for pH-sensitive field-effect transistors based on two-dimensional (2D) materials. The electrostatics along the electrolyte-gated 2D-semiconductor stack is treated by solving the Poisson equation including the Site-Binding model and the Gouy-Chapman-Stern approach, while the carrier transport is described by the drift-diffusion theory. The proposed model is provided in an analytical form and then implemented in Verilog-A, making it compatible with standard technology computer-aided design tools employed for circuit simulation. The model is benchmarked against two experimental transition-metal-dichalcogenide (MoS2 and ReS2) based ion sensors, showing excellent agreement when predicting the drain current, threshold voltage shift, and current/voltage sensitivity measurements for different pH concentrations.

Fig: a) Schematic depiction of a 2D-ISFET b) its quivalent capacitive circuit

Acknowledgments: This work is supported in part by the Spanish Government under the projects TEC2017-89955-P, RTI2018-097876-B-C21 and PID2020-116518GB-I00 (MCIU/AEI/FEDER, UE); the FEDER/Junta de Andalucía under project BRNM-375-UGR18; EC under Horizon 2020 projects WASP No. 825213 and GrapheneCore3 No. 881603. E.G. Marin gratefully acknowledges Juan de la Cierva Incorporación IJCI-2017-32297. A. Toral-Lopez acknowledges the FPU program (FPU16/04043). F. Pasadas acknowledges funding from PAIDI 2020 and Andalusian ESF OP 2014-2020 (20804). F. Pasadas and D. Jiménez also acknowledge the partial funding from the ERDF allocated to the Programa Operatiu FEDER de Catalunya 2014-2020, with the support of the Secretaria d’Universitats i Recerca of the Departament d’Empresa i Coneixement of the Generalitat de Catalunya for emerging technology clusters to carry out valorization and transfer of research results. Reference of the GraphCAT project: 001-P-001702.

[paper] Verilog-A Ion Sensitive FET for pH Sensor

Megha Agrawal, Nidhi Agrawal, Alpana Agarwal and Anil K. Saini*

Modeling of Ion Sensitive Field Effect Transistor for pH Sensor using Verilog-A

 Recent Advancement in Communication System & Image Processing

RACISP-2012 at: BKBIET, Pilani

Thapar University, PATIALA – 147004, Punjab

*Central Electronics Engineering Research Institute, PILANI – 333031, Rajasthan

Abstract: ISFET semiconductor technology enables the design of true solid state pH sensor. An ISFET can be modeled by considering it as two fully uncoupled stages: an electronic stage i.e., the MOSFET which is the starting structure of the ISFET and an Electro-chemical stage i.e., the electrolyte–insulator interface which is pH dependent. This paper describes the modeling of ISFET for pH measurement using Verilog A which is compatible with cadence environment. Any change in pH directly affects the threshold voltage of ISFET. To measure this change in pH, ISFET is configured in such a way so that change in threshold voltage can be directly detected. For this purpose a sensing read-out has been designed using Gate complementary ISFET/MOSFET pair (CIMP) technique. Simulated result shows good linearity between output voltage of sensing readout circuit with pH variation for the range of 1 to12. The ISFET is thermally instable due to semiconductor properties and pH dependency on temperature, which in turn affects the pH reading of the solution at a temperature other than room temperature with slope of +0.69mV/0C, +1.25mV/0C and +1.60mV/0C respectively for pH= 4, for pH=7 and for pH=10.

Fig: a) n-channel ISFET structure and b) its equivalent electric circuit [ref]

Acknowledgment: The work is financially supported by Department of Information Technology, Ministry of Communication & Information Technology, Government of India, under SMDP-VLSI (Phase II) project.

[ref] Sergio Martinoia, Giuseppe Massobrio, “A Behavioral Macromodel of the ISFET in SPICE,” Sensors and Actuators B, Vol. 62, pp. 182–189, 2000

Appendix A

// Verilog-A Code for ISFET [ref]
`include "constants.vams"
`include "disciplines.vams"
module ISFET(ref,gm,ph);
inout ref,gm,ph;
electrical ref,gm,ph;
real EPH;
real T;
electrical node;

electrical x,y;
// PARAMETERS FOR ISFET

parameter real NAv = 6.023E26; //Avogadros constant(1/MOLE)

// ISFET geometrical parameters

parameter real DIHP =0.1E-9;

parameter real DOHP =0.3E-9;

//ISFET electrochemical parameters

parameter real KA = 15.8;

parameter real KB = 63.1E-9;

parameter real KN = 1E-10;

parameter real Nsil = 3.0E+18;

parameter real Nnit = 2.0E+18;

parameter real Cbulk = 0.1;

parameter real epso = 8.85E-12;

parameter real epsihp = 32; //relative permittivity of the Inner Helmholtz layer

parameter real epsohp = 32; //relative permittivity of the Outer Helmholtz layer

parameter real epsw = 78.5; //relative permittivity of the bulk electrolyte solution

//Reference-electrode electrochemical parameters

parameter real Eabs = 4.7; //absolute potential of the standard hydrogen electrode

parameter real Erel = 0.2;

parameter real Phim = 4.7; //work function of the metal back contact

parameter real Philj = 1E-3; //liquid-junction potential difference between the ref

solution and the electrolyte

parameter real Chieo = 3E-3; //surface dipole potential

real ET; //THERMAL COFFICIENT
real sq;
real CH, CD, CEQ, CB;
real Eref;

analog begin

T= $temperature;

ET= (`P_Q /(`P_K * T));

sq = sqrt(8*`P_EPS0*epsw*`P_K * T);

CB = (NAv*Cbulk);

CH = ((`P_EPS0*epsihp*epsohp) / (epsohp*DIHP + epsihp*DOHP));

CD = (sq*ET*0.5)*sqrt(CB);

CEQ = 1/(1/CD + 1/CH);

V(ref,node) <+ Eabs - Phim - Erel + Chieo + Philj;

Eref = V(ref,node);

V(x)<+ log(KA*KB)+4.6*V(ph);

V(y)<+ log(KA)+2.3*V(ph);

V(gm,node) <+ (`P_Q / CEQ) * (Nsil * ((limexp(-2 * V(gm,node) * ET)– limexp

(V(x))) / (limexp(-2 * V(gm,node) * ET) + limexp(V(y)) * limexp(-1 * V

(gm,node)*ET) + limexp(V(x)))) + Nnit*((limexp(-1 * V(gm,node)*ET))/(limexp(-1* V(gm,node)*ET)

+ (KN/KA) * limexp(V(y)))));

end

capacitor #(.c(CEQ)) Cq(node,gm);

resistor #(.r(1G)) RP1(x,gnd);

resistor #(.r(1G)) RP2(y,gnd);

resistor #(.r(1k)) RPH(ph,gnd);

endmodule

[chapter] Design of FET Biosensors

Khuraijam Nelson Singh¹ and Pranab Kishore Dutta¹

Chapter 8: Analytical Design of FET-Based Biosensors

in Advanced VLSI Design and Testability Issues; Eds: Suman Lata et all.

CRC Press, 19 Aug 2020; 360 pages

¹NERIST, Arunachal Pradesh, India

Abstract: Research on biosensors has seized the interested researchers over the past few decades due to their various advantages and applications. They are used in the discovery of drugs, monitoring of diseases, agriculture, food quality control, industrial wastage monitoring, military, etc. The sensing analyte is the main element that differentiates a biosensor from the other physical/chemical sensors. In general, the biosensor is a device that is used to detect an analyte using a biosensitive receptor. Its main components are as follows:

• Analytes: The substance that is intended to be detected, such as glucose in a glucose sensor, ammonia in ammonia sensor, and so on.
• Bioreceptors: The bioreceptors are biosensitive elements used to detect target analytelbiomolecule. They are sensitive to the analytes of interest. Some examples of bioreceptors are antigen, DNA, enzyme, and so on.
• Transducers: The elements that are used to convert energy from one form to another are called transducers. In a biosensor, the interaction of analytes and bioreceptors produces changes in the form of heat, gas, light, ions, or electrons. These changes are then converted into a quantif‌iable form by the transducer. Usually, the output of the transducer is in the form of electrical or optical signals, and the generated signal is proportional to the interaction between the analyte and the biosensor.

FIG: Schematic diagram of ion-sensitive f‌ield-effect transistor (ISFET)

ENBIOS-2D Lab

Aldi Hoxha1, Paolo Scarbolo1, Andrea Cossettini2, Federico Pittino3, Luca Selmi4

1. DPIA, Università degli Studi di Udine 2. University of Udine 3. Università di Udine 4

DPIA, Università degli Studi di Udine, Italy

Abstract: ENBIOS-2D Lab is a tool to illustrate and to study simple Ion Sensitive Field Effect Transistor structures in two dimensions. Together with its companion tool ENBIOS-1D Lab, it is meant for use as a teaching tool in support of undergraduate or graduate courses on the basic physics of transduction in ion and particle sensors, and to assist early stage researchers getting familiar with some basic concepts in the field. At the present stage, ENBIOS-2D Lab supports simulation and visualization of DC I-V characteristics, impedance/admittance spectra as well as DC and AC potential/carrier/ion distributions in simple two-dimensional ISFET structures. A broader set of case studies will become available with future releases of the tool. The companion ENBIOS-1D Lab tool offers the possibility to simulate simple Electrolyte/Insulator/Semiconductor systems in one-dimension. The physical system is modelled with the Poisson/Boltzmann (DC) and Poisson/Nernst/Planck - Poisson/Drift/Diffusion (AC small signal) equations coupled to the site-binding charge model equations at the Electrolyte/Insulator interfaces. Dedicated models are implemented for the frequency and salinity dependence of the electrolyte electrical permittivity and the temperature dependence of the ions' mobility (in water solvent). ENBIOS-2D Lab is powered by ENBIOS, (Electronic Nano-BIOsensor Simulator), a general purpose three-dimensional Control Volume Finite Element Method (CVFEM) simulator developed in-house at the University of Udine - Italy. ENBIOS simulates in three dimensions (3D) the DC and AC small signal impedance response to ions and micro/nanoparticles of three-dimensional devices made of semiconductor, insulator and electrolyte materials.

References:

[1] P. Scarbolo, E. Accastelli, F. Pittino, T. Ernst, C. Guiducci, L. Selmi, “Characterization and modelling of differential sensitivity of nanoribbon-based pH-sensors”, Proceedings of the 2015 Transducers - 18th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS), 21-25 June 2015, pp. 2188-2191

[2] Paolo Scarbolo, Enrico Accastelli, Thomas Ernst, Carlotta Guiducci and Luca Selmi, "Analysis of Dielectric Microbead Detection by Impedance Spectroscopy with Nanoribbons", IEEE Nano Conference, August 2016.

[3] Federico Pittino and Luca Selmi, "Use and comparative assessment of the CVFEM method for Poisson–Boltzmann and Poisson–Nernst–Planck three dimensional simulations of impedimetric nano-biosensors operated in the DC and AC small signal regimes", Comput. Methods Appl. Mech. Engrg., v.278, (2014), pp.902–923.