Threshold Voltage Sensitivity Research Articles

Dielectric Modulated Nanotube Tunnel Field-Effect Transistor with Core-Shell Cavity as a Label-Free Biosensor: Proposal and Analysis.

Dielectric Modulated Field-Effect Transistors (DMFETs) have emerged as promising candidates for label-free bioanalyte detection. However, the inherent short-channel effects in conventional DMFETs increase their static power dissipation significantly and limit their scalability and sensitivity. Therefore, FETs based on alternate conduction mechanism such as tunneling (TFETs), which are immune to the short-channel effects, appear to be a lucrative alternative to the MOSFETs for biosensing application. In this work, we propose a novel Dual Cavity Dielectric Modulated Nanotube Tunnel FET (DCDM NTTFET)-based label-free biosensor consisting of a Ge source and nanocavities within the core as well as a shell gate stack, which not only outperforms the conventional MOSFET and advanced nanowire (NW) TFET-based biosensors in terms of energy-efficiency and scalability but also exhibits a significantly high drain current sensitivity (SION = 2.9 × 108) and a threshold voltage sensitivity (SVth = 0.85), and a considerably high selectivity of more than 6 orders of magnitude. We also perform a comprehensive design space exploration for the proposed DCDM NTTFET and provide necessary design guidelines to further improve its performance considering the practical artifacts such as steric hindrance.

An embedded gate gate-all-around FinFET for biosensing application

A dielectric modulated embedded gate gate-all-around fin field-effect transistor (EGGAA-FinFET) has been proposed for label-free detection applications of biomolecules in this article. The design expands the biomolecule capture area by establishing a cavity below the embedded gate. The performance of EGGAA-FinFET and FinFET biosensors is analyzed in a comprehensive comparison in terms of electrical performance, sensitivity and selectivity. Some important biosensing characteristics for EGGAA-FinFET (FinFET) have been calculated to be 0.43 V (0.32 V) for threshold voltage sensitivity, 2.22 × 106 (8.32 × 104) for current switching ratio sensitivity, and 0.75 (0.65) for subthreshold swing sensitivity. To determine the optimal structure of the biosensor, the effect of structural parameters on sensitivity is investigated. In addition, the effect of the filling factor on the biosensor is considered. The real-world performance of biosensors is assessed using the linearity parameter, showing that the EGGAA-FinFET biosensor has better noise resistance compared to the FinFET biosensor.

DM-PA-CNTFET Biosensor for Breast Cancer Detection: Analytical Model

In this paper, an analytical model for a novel design dielectric modulated plasma-assisted carbon nanotube field-effect transistor (DM-PA-CNTFET) biosensor is proposed for breast cancer detection. This work is based on a PA-CNTFET in which CNT is used as a channel of FET, and various other device engineering techniques such as dual metal gate-all-around structure and dielectric stack of SiO2 and HfO2 have been used. A comparative analysis of DS-GAAE-CNTFET was performed using a silicon gate all-around FET (Silicon-GAA-FET)-based biosensor. Early detection of breast cancer is made possible by immobilizing MDA-MB-231 and HS578t into the dual-sided nanocavity, which alters the electrical properties of the proposed CNTFET-based biosensor. The DS-GAAE-CNTFET sensor demonstrates a drain ON current sensitivity of 236.9 nA and a threshold voltage sensitivity of 285.58 mV for HS578t cancer cells. Malignant MDA-MB-231 breast cells exhibit a higher drain ON current sensitivity of 343.35 nA and a corresponding threshold voltage sensitivity of 293.23 mV. The exceptional sensitivity and structural resilience of the DS-GAAE-CNTFET biosensor establish it as a promising candidate for early breast cancer detection.

A P+ pocket doped 4H–SiC Schottky barrier FET as highly sensitive label-free biosensor

In this paper, a 4H–SiC Schottky barrier field-effect transistor with a P+ doping Pocket based on dielectric modulation effect for label-free detection of biomolecules has been proposed. Upon optimization of the length and position of P+ doping pocket, the sensitivity of the biosensor achieves the maximum when it is located within the channel 1 nm away from the Schottky contact with a length of 5 nm. Simulations have been performed for different dielectric constants and biomolecules with different charge densities by Sentaurus TCAD. The results show that the new structure has an on-current sensitivity of 1.03 × 108, a maximum transconductance sensitivity of 6.24 × 107, a threshold voltage sensitivity of 65 mV, and an Ion/Ioff ratio sensitivity of 1.8 × 104 for neutral biomolecules with K = 12. In addition, the fill factor of the cavity and linearity of the proposed structure are considered in this paper. Further, the on-current sensitivity of our proposed structure is gauged against state of the art, which demonstrate a high sensitivity of our proposed biosensors. The smaller size and prominent sensitivity characteristics of the biosensor proposed in this paper have made it widely used in the field of biomedical detection that requires high integration and efficient detection.

Threshold voltage model development of N+ pocket vertical junctionless TFET (V-JL-TFET) as a label free biosensor

This work investigates into the potential application of an improved N+ pocket Vertical Junctionless TFET (V-JL-TFET) as a label free biosensor. To calculate the sensitivity of the biosensor, an analytical model based on device physics was developed that accounts for the impact of both charged and uncharged biomolecules on the threshold voltage (Vth). As a result, the developed model offers a solution that is applicable for both uncharged and charged biomolecules. This model demonstrates a strong agreement with the experimentally determined threshold voltage (Vth) obtained from simulation results. Furthermore, sensitivity is obtained by assessing the shift in threshold voltage (Vth) resulting from changes in the dielectric constant. It's observed that Vth increases with decrease in dielectric value. The Vth value with empty nanogaps has been used as a reference point. Finally, the sensitivity of gate threshold voltage was calculated, and the obtained values are high enough to detect both charged and uncharged biomolecules. A detailed analysis of Selectivity, Linearity, stability and reliability of the proposed Biosensor is also presented.

Study of ISFET for KCl sensing

This work presents the fabrication and electrical characterization of the Ion Sensitive Field Effect Transistor (ISFET) exposed to potassium chloride (KCl) solutions. The focus of the study is to compare two measurements methods and verify the effects of these methods in the device threshold voltage (VTH) sensitivity to the different KCl concentrations. First, a reference electrode (a platinum needle) is placed in the sample solution over the gate area of the device, demonstrating that the threshold voltage decreases with the increase of the KCl concentration. The method shows a sensitivity of 10.44 mV/mM for the low KCl concentration range (0 to 10 mM) and 0.5 mV/mM for the higher KCl concentration range (10 to 100 mM). The second method involves inserting a second platinum electrode into the solution on the field oxide. This method proposes the KCl electrolysis to increase the selectivity for potassium ions. The result allows the next steps for potassium sensing biosensor application with selective membranes.

Sensitivity enhancement using triple metal gate work function engineering of junctionless cylindrical gate all around SiNW MOSFET based biosensor for neutral biomolecule species detection for upcoming sub 14 nm technology node

In the present work Dielectric Modulation (DM) technique along with Triple Metal (TM) gate engineering has been used for the junctionless (JL) cylindrical gate all around (CGAA) Si nanowire (NW) MOSFET based biosensor for label free electrical detection of neutral biomolecules species like Uricase, Streptavidin, Protein, Biotin, ChOx (choline oxidase), and APTES etc. For this device, the Drift Diffusion approach has been used along with self-consistent solution of Schrodinger’s equation with Poisson’s equation. For the biomolecule immobilization, a nanogap cavity region is formed in the JL SiNW MOSFET by etching gate oxide layer above the SiO2 interfacial layer. The change in the drain current (ID), threshold voltage (Vth), off-current sensitivity (SIoff), threshold voltage sensitivity (SVth) and Ion/Ioff current ratio of the device have been considered as the sensing parameters for detection of biomolecules under dry environment condition. In present work a new sensing metric of sensing of biomolecules – DIBL has been added which has never been reported in literature. In this work for JL SiNW, sensitivity metrics like smaller DIBL ∼50.47 mV/V, higher SIoff9.33×105, higher SVth28.72, nearly ideal subthreshold slope (SS) ∼60 mV/dec, and higher Ion/Ioff current ratio ∼9.01 × 1012 have been obtained in comparison to available literature results.

Design and Simulation of Dielectrically Modulated Dual Material Gate-Stack Double-Gate FinFET Biosensor

This study developed and evaluated a dual-material gate stack double-gate FinFET-based biosensor (DM-GS-DG FinFET). The device was dielectrically modulated and investigated for molecules, such as streptavidin, gluten, zein, hen egg-white lysozyme, and acetylene tetrabromide, based on current, threshold voltage, subthreshold swing, and switching sensitivity. The influence of charged and neutral biomolecules within the nanocavity on the electric, analog, and radiofrequency parameters was recorded. This study was conducted relative to different dielectric κ-values of 12 in terms of the percentage sensitivity improvement (SI%). The results reveal that the percentage of sensitivity ION improves effectively, especially for low κ-values, compared with other sensitivity measures. All the sensitivity evaluations indicated that DM-GS-DG-FinFET combined with biomolecules is a viable option for biosensing purposes.

A Theoretical Approach to Study the Frequency Dependent Dielectric behavior of Breast Cancer Cells using AlN buffer-based AlGaN/GaN HEMT

Abstract This article investigates the applicability of open gated high electron mobility transistor (HEMT) as a biosensing platform for Breast cancer detection. The present study reports the detection of healthy (MDA-10) and malignant cells (MDA-MB-231) associated with breast cancer using high-quality AlN buffer AlGaN/GaN HEMT with dual cavity structure formed by etching out the gate metal from source and drain sides under the gate region. The AlN buffer AlGaN/GaN HEMT provides better 2DEG confinement and large conduction band offset than GaN buffer. The proposed design is analyzed at frequencies of 900 MHz and 10 GHz, as breast cells have distinct dielectric properties at different microwave frequencies. The variation in dielectric constant of the cavity region corresponding to biomolecular species will change the device’s electrical characteristics and hence can be used to detect breast cancer cells. In this work, the device sensing parameters considered for analysis are shift in threshold voltage and drain current sensitivity. The device performance has also been analyzed by optimizing cavity thickness and length to select the best design for the sensing. The effect of non-ideal conditions such as steric hindrance and probing is also studied by emulating these real time effects in simulation. The device shows a maximum drain current sensitivity of 29.94% for 20 nm of cavity thickness and 1µm of the cavity length. The results depict that the proposed device design exhibits a highly sensitive response and can be promising alternate for future biosensing applications.

Sensitivity improvement in gate engineered technique dielectric modulated GaN MOSHEMT with InGaN notch for label-free biosensing

This paper focuses on the impact of gate-engineered dielectric-modulated GaN MOSHEMT with InGaN notch on sensitivity enhancement for label-free biosensing. The novelty of this study utilizes the charge-plasma effect induced by the dual metal gate (DMG) technology adopted to realize the effect of sensitivity on different biomolecules. Moreover, the presence of an InGaN notch enhances carrier confinement in the 2DEG, subsequently improving the threshold voltage and device sensitivity at the AlGaN/GaN interface. The maximum drain current, IDS of 4.602 A mm−1, transconductance, gm of 18 mS/mm, and sensitivity has been improved by around 61% for the Uricase biomolecule by introducing the dual metal gate technology. The work function difference of the two metal gates suppresses the Short Channel Effects (SCEs) and hot carrier effects in DMG MOSHEMT, thereby screening the drain potential variations by the gate near the drain. In addition, increased carrier transport efficiency results from a more consistent electric field along the channel. All the simulations are carried out using the Sentaurus TCAD simulator, and the results imply the feasibility of gate-engineered GaN MOSHEMT for label-free biosensing.

Sensitivity estimation of biosensor in a tapered cavity MOSHEMT

The present research provides a comprehensive investigation of the structural modification at the cavity under the gate (CUG) on the metal oxide semiconductor high electron mobility transistor (MOSHEMT)-based biosensor by projecting its basic figures of merit (FOMs). The effect of a tapering dielectric on the sensitivity of the biosensor has not been extensively investigated in many research efforts. Therefore, to account for the larger binding surface, the current study considers a wide range of permittivity of the biomolecules from 1 to 10, using the dielectric modulation technique in the tapered cavity. Various cavities are analysed to enhance the sensitivity. The findings indicate that the presence of biomolecules causes a considerable fluctuation in the drain current, threshold voltage, on-current, off-current, channel potential, and oxide capacitance. It has also been estimated how various fill percentages and charged and neutral biomolecules affect the device’s sensitivity. The tapered dielectric MOSHEMT offered an on-current sensitivity and threshold voltage sensitivity of 1.25 and 0.889 for neutral biomolecule (k = 8) and 0.562 and 2.23 for positively charged biomolecule respectively. Thus, tapering of the oxide does offer better sensitivities that can be exploited for biosensing applications.

Dielectrically modulated hetero‐material double gate tunnel field‐effect transistor for label free biosensing

AbstractThis work proposes a novel double gate hetero‐material tunnel field effect transistor for label free biosensing applications. The device consists of III‐V semiconductor gallium arsenide (GaAs) which serves as a substrate. Source and drain regions made of Germanium are used due to its compatibility with GaAs. Cavities of 15 × 1.5 nm are created near source‐channel junctions for the biomolecules to be placed in. The ION sensitivity of 2.23 × 106 for neutral biomolecules has been obtained from 2D simulations using ATLAS TCAD software. Furthermore, transconductance sensitivity of 2.27 × 106, ION/IOFF sensitivity of 2.46 × 105, subthreshold swing (SS) sensitivity of 28.6 mV/decade and threshold voltage sensitivity of 1.2 mV for neutral biomolecules is obtained. The ION sensitivity of 3.93 × 106 and 1.42 × 106 for positively and negatively charged biomolecules respectively has been obtained. Also, SS sensitivity of 28.3 and 28.8 mV/decade for positively and negatively charged biomolecules respectively has been observed. ION sensitivity shows that the proposed device is 1000× better than the conventional one.

Gate electrode stacked source/drain SON trench MOSFET for biosensing application

This work inspects a dielectrically modulated (DM) stacked source/drain SiGe dual-metal trench gate silicon on nothing (SON) metal–oxide–semiconductor field-effect transistor (SiGe-DMTG SON MOSFET) biosensor to enhance the sensing capability of the device. A nano-cavity is implanted in the either side of gate area for immobilization of biomolecules which can modulate the gate capacitance and dielectric constant of the nanocavity area. Thus the device undergoes a threshold voltage shift which has a great impact on device sensitivity. So SiGe-DMTG SON MOSFET biosensor is proposed to identify the sensing performance of various analytes like Uricase (k = 1.54), Streptavidin (k = 2.1), Biotin (k = 2.63), 3-aminopropyltriethoxysilane (APTES) (k = 3.57) and protein (k = 8) using DM technique. The electrostatic properties of the neutral biomolecules such as electrostatic potential, electric field, On current, switching ratio, threshold voltage, On current sensitivity, threshold voltage sensitivity, and subthreshold performance of SiGe-DMTG SON MOSFET biosensor have been evaluated using 2D ATLAS device simulator. Further, the parasitic capacitances of the proposed biosensor has been investigated for different biomolecules in the nano-cavity region in order to observe the sensing performance of the device. From the result analysis it has been observed that for protein (k = 8), the proposed SiGe-DMTG SON MOSFET biosensor offers a threshold voltage sensitivity of 0.581 and On current sensitivity of 1.765. Apart from this, protein (k = 8) offers a strong threshold voltage shift of 104.8 mV with respect to k = 1 shows best suited for biosensing application.

Analytical modeling and numerical simulation of graded JAM Split Gate-All-Around (GJAM-SGAA) Bio-FET for label free Avian Influenza antibody and DNA detection

This manuscript presents the analytical model of a novel biosensor called Graded JAM Split Gate-All-Around (GJAM-SGAA) Bio-FET for the detection of Avian Influenza antibody and DNA. The GJAM-SGAA Bio-FET utilizes a silicon Gate-All-Around FET which operates in the Junctionless Accumulation Mode (JAM), with a graded doping in the channel. This Bio-FET also features a gate underlap double sided cavity that enables detection of biomolecules without the use of labels. Gate underlap cavities overcome the fabrication complexity of nanocavities and provides structural stability. A comparative analysis between the GJAM-SGAA Bio-FET and non-graded JAM Split Gate-All-Around FET (SGAA-FET) demonstrates that the proposed BioFET has 5.72 times higher ION current sensitivity, 5.3 times increase in threshold voltage sensitivity (SVth), and 2.13 × 102 times improvement in switching ratio sensitivity for avian influenza biomolecule. The SVth of proposed biosensor is compared with the existing biosensors and found that a triple-metal engineered gate and graded doped channel substantially boosts the sensitivity of proposed biosensor.

Threshold and surface potential-based sensitivity analysis of symmetrical double gate AlGaN/GaN MOS-HEMT including capacitance effects for label-free biosensing

This paper presents an analytical framework, based on the surface potential for a symmetrical double-gate AlGaN/GaN Metal oxide semiconductor high electron mobility transistor (DG-MOSHEMT) equipped with an embedded nanocavity tailored for biomedical sensing applications. The proposed model operates on the dielectric modulation principle and meticulously scrutinizes the device’s performance using critical sensing metrics such as threshold voltage shift (ΔVth), threshold voltage sensitivity (SVth), surface potential shift (ΔΨs,0), and surface potential sensitivity (SΨs,0). The model demonstrates remarkable sensitivity in detecting minute biomolecule variations, explicitly focusing on streptavidin, uricase, protein, and ChOx as the target biomolecules. Additionally, analytical equations based on surface potential are established to accurately determine gate charges (QG), gate-to-drain capacitance (CGD), and gate-to-source capacitance (CGS). The thorough investigation of biomolecule effects on gate capacitance holds paramount significance as it plays a vital and profound role in dictating device performance. Furthermore, variations in nanocavity length, AlGaN layer thickness, and oxide layer thickness are explored to understand their influence on ΔVth and SVth. The proposed model exhibits a remarkable improvement in both threshold voltage shift and sensitivity compared to the single MOS-HEMT. Notably, it demonstrates substantial enhancements of 2.06, 1.72, 1.49, and 1.5 times for the uricase, streptavidin, protein, and ChOx biomolecules, in terms of threshold voltage shift, and impressive improvements of 10.7%, 14.5%, 18.2%, and 50% for the same biomolecules, respectively, in terms of threshold voltage sensitivity, surpassing the previous findings. Uricase exhibited the most significant shift in surface potential (ΔΨs,0) among the analyzed biomolecules, with a value of 100 mV mm−1 and a sensitivity (SΨs,0) of 0.44. In contrast, ChOx showed a modest (ΔΨs,0) of 24 mV mm−1 with a relative sensitivity (SΨs,0) value of 0.108. Increasing nanocavity length and oxide layer thickness positively contribute to ΔVth and SVth. Moreover, while an increase in AlGaN layer thickness enhances ΔVth performance, its impact on SVth is minimal.

Inverse Gaussian Doped Nanoscale Junctionless Gate All Around-based Biosensor

This article discusses the electrical properties of an Inverse Gaussian Junctionless Gate All Around (IG-JLT-GAA) field effect transistor for identifying neutral and charged bioanalytes. In this work, the inverse Gaussian doping profile enables the potent command of gate over charge in channel in the GAA structure, resulting in improved performance attributes such as OFF current, ON current, current ratio, subthreshold slope, drain-induced barrier lowering, threshold voltage, and transconductance for the proposed biosensor. The leakage current (OFF) is 10−17 A, and the drain current (ON) is 10−6 A, with their ratio of 10−11 fetched at K = 10. This article investigates the effect of varying dielectric constants of biomolecules immobilized in cavity reflects the enhancement in biosensor sensitivity due to the immobilization of high dielectric constant protein bioanalytes. The drain-induced barrier lowering (DIBL) and subthreshold swing (SS) are 4.4 mV/V and 60.6688 mV/dec, respectively, for K = 10. The estimated threshold voltage sensitivity (SVT ) for various dielectric constant biomolecules was found to be 9.7 and 110.5 mV for K = 1 and K = 10, respectively. Further, the performance of the biosensor using well-known biotin biomolecules with K = 2.63 is studied, and the result shows that the biosensor performs outstandingly in all performance attributes required for the detection of charged and neutral biomolecules.

2D analytical modelling of asymmetric junctionless dual material double gate MOSFET for biosensing applications considering steric hindrance issue

The current manuscript for Asymmetric Junctionless Dual Material Double Gate MOSFET (AJDMDG MOSFET) biosensor reports improved sensitivity for both threshold voltage and ON-current. In the presence of high-K dielectric material, the device was built using both neutral and charged biomolecules. After calculating the minimal surface potential, the threshold voltage is calculated by solving the 2D Poisson’s equation using a parabolic-potential configuration under realistic boundary circumstances. Analytical results show good agreement with TCAD simulation, prompting an exploration of threshold voltage sensitivity with front-gate voltage changes of all possible dimensions. Corresponding drain current sensitivity with a higher ON-to-OFF current ratio is theoretically estimated and compared with identical DGFET architecture, resulting in a significant improvement for all possible step patterns when steric hinderance is considered for moderately filled cavities; this aids in detecting both labelled and label-free electrical species at lower concentration levels.

Investigation of palladium gated polarity controllable FET as a highly sensitive and robust hydrogen gas sensor

AbstractThe paper investigates the design and performance of a novel palladium gated‐polarity controllable Field Effect Transistor (FET) (PC‐FET) for hydrogen gas sensing applications. In the present work, catalytic sensing metal gate (palladium) is chosen as control gate (CG) and hydrogen gas molecules are exposed on the region controlled by CG. A compact analytical model has been derived for PC‐FET based sensor and the performance of the proposed gas sensor has been examined in terms of energy band profile, surface potential, electric field, transfer characteristics and transconductance and the derived analytical results are verified using TCAD simulated results. Furthermore, the sensitivity metrics such as threshold voltage sensitivity, drain current sensitivity, transconductance sensitivity and ION/OFF sensitivity have also been extensively investigated for both modes of proposed sensor for a wide range of pressure that is, 10−14–10−8 Torr.

Highly sensitivity Non-Uniform Tunnel FET based biosensor using source engineering

The manuscript proposes a novel dielectrically modulated Non-Uniform Tunnel FET based Biosensor for the detection of charged and neutral biomolecules. In this work, the reliability analysis of Dual Material Source based Non-Uniform Tunnel FET Biosensor has been performed. The design of Non-Uniform Tunnel FET and doping profile at the tunneling junction is accountable for the improved sensitivity. The response of the proposed biosensor has been analysed in terms of threshold voltage sensitivity, ON-OFF current ratio sensitivity and drain current sensitivity by using Sentaurus TCAD device simulator. The investigation includes analysis of neutral, positive and negatively charged Bio-analytes at immobilization layer for different cases of dielectrics. In case of positively charged Bio-analytes, it has been observed that the proposed biosensor can obtain the highest sensitivities of 100 mV, 7.9 × 106, 451 for threshold voltage, ON-OFF current ratio, and drain current sensitivities, respectively. Furthermore, the performance and reliability assessment of the biosensor have been considered using the appearance of steric hindrance in different patterns and temperature fluctuations in the wide range from 200 K to 400 K.

180 nm FLASH ANALOG TO DIGITAL CONVERTOR

In this paper, Threshold Inverter Quantizer (TIQ) is a novel idea which can effectively replace the reference voltage generator, resistive/capacitive voltage divider network and array of differential comparators in a conventional flash Analog to Digital Converter (ADC) by an internal reference comparator array constructed of Complementary Metal Oxide Semiconductor (CMOS) inverters. The inverter threshold voltage serving as the reference voltage, this architecture claims large improvements in terms of silicon area, power consumption and operating speed. Perturbations due to sensitivity of the inverter threshold voltage to operating temperature/process variations pose impediments in such ADC designs and strongly demand a compensation scheme to such variations. This paper presents a TIQ based flash ADC, with inverter threshold voltage compensation. In this project 5 bit flash adc using TIQ Comparator is designed and simulated using TANNER EDA in 180nm technology. Key Words: flash, adc, tiq(threshold inverter quantization)