Figure 1 - available from: Scientific Reports
This content is subject to copyright. Terms and conditions apply.

# Schematic illustration of the dimensions of transistor-based biosensors compared to typical biological systems, as well as the impact of such dimensions on the sources of noise in such devices.

Source publication
Article
Full-text available
Transistor biosensors are mass-fabrication-compatible devices of interest for point of care diagnosis as well as molecular interaction studies. While the actual transistor gates in processors reach the sub-10 nm range for optimum integration and power consumption, studies on design rules for the signal-to-noise ratio (S/N) optimization in transisto...

## Contexts in source publication

Context 1
... for genome sequencing 1 . They are still being further integrated for statistical study 1,2 , pico-or nano-liter volume analysis 3-5 or singlemolecule sensing 6,7 . Smallest nanotransistor-based biosensors are very similar to mass-production state-ofthe-art semiconductor transistors 8,9 , have dimensions close to small biological objects (see Fig. 1), and tend to have a very low charge noise S q . In particular, the sub-elementary charge or single-charge sensitivity ability in liquid 10 is promising for the development of the non-optical version of single-molecule digital nanoarrays 11 , or nanoelectrochemistry 12 . In contrast, larger devices, whose dimensions are typically ...
Context 2
... a very low charge noise S q . In particular, the sub-elementary charge or single-charge sensitivity ability in liquid 10 is promising for the development of the non-optical version of single-molecule digital nanoarrays 11 , or nanoelectrochemistry 12 . In contrast, larger devices, whose dimensions are typically similar to a biological cell (see Fig. 1), have a larger charge noise but tend to have a very low input-referred voltage noise S V G . Several studies have recently investigated quantitatively the role of gate area A for S V G noise 13,14 in the range A > 1 µm 2 . In principle, S V G reflects the smallest change in analyte concentration that can be detected with such ...
Context 3
... increases by up to two orders of magnitude when compared to no trap for both N-type and P-type devices due to a random-telegraph signal (RTS) noise whose amplitude �I = g m × q * /(C G × A) , where q * being an effective charge of about 0.5q for SiO 2 that accounts for image charge effects 19 . RTS noise has a Lorentzian power spectrum shape (see Fig. 1) that can be evaluated as 19 ...

## Citations

... We have used lightly doped thin device layer SOI wafers to demonstrate their suitability for detecting small changes in charge at the electrolyte-oxide surfaces (i.e., caused by the interaction of the proteins with peptides immobilized on the gate surface, which is the long-term goal of this work). A larger planar surface area allows a better signal-to-noise ratio and also less stringent requirements to counter reliability issues, e.g., from pin-holes, as compared to the nanowire counterparts [21]. Figure 1 shows the schematic of the proposed device design ( Figure 1A) and the cross-sectional view of the device layout ( Figure 1B). ...
Article
Full-text available
Label-free field-effect transistor-based immunosensors are promising candidates for proteomics and peptidomics-based diagnostics and therapeutics due to their high multiplexing capability, fast response time, and ability to increase the sensor sensitivity due to the short length of peptides. In this work, planar junctionless field-effect transistor sensors (FETs) were fabricated and characterized for pH sensing. The device with SiO2 gate oxide has shown voltage sensitivity of 41.8 ± 1.4, 39.9 ± 1.4, 39.0 ± 1.1, and 37.6 ± 1.0 mV/pH for constant drain currents of 5, 10, 20, and 50 nA, respectively, with a drain to source voltage of 0.05 V. The drift analysis shows a stability over time of −18 nA/h (pH 7.75), −3.5 nA/h (pH 6.84), −0.5 nA/h (pH 4.91), 0.5 nA/h (pH 3.43), corresponding to a pH drift of −0.45, −0.09, −0.01, and 0.01 per h. Theoretical modeling and simulation resulted in a mean value of the surface states of 3.8 × 1015/cm2 with a standard deviation of 3.6 × 1015/cm2. We have experimentally verified the number of surface sites due to APTES, peptide, and protein immobilization, which is in line with the theoretical calculations for FETs to be used for detecting peptide-protein interactions for future applications.
... A time trace of the 4-nanowire one and its amplitude evolution versus Vds and Vg are shown in Figure 2. The relative amplitude was as high as 15% of the overall current (Ids vs. Vg in the inset of Figure 3a), i.e., as high as 60% of the current flowing in the nanowire holding the defect. This RTS amplitude was extremely large when compared to 6 the RTS usually obtained in nanotransistors 33,34 . The evolution of the time spent in the up state (up) or down state (down) showed no correlation with Vg ( Figure S5) but demonstrated a clear ...
Article
The role of a single defect on the performance of transistors must be better understood to improve the design and fabrication process of nanotransistors. Capacitive networks on 18 nm long gate junctionless (JL) vertical gate-all-around nanowire transistors are studied through random telegraph signals, with amplitudes as high as 60% for a single nanowire. Defect densities extracted from both JL and accumulation-mode transistors allows one to discuss number fluctuation-based noise models, questioning the significance of defect densities of less than one defect per nanodevice. It is shown that the consideration of an effective charge in the models solves this issue.
... The advancement of semiconductor technology has led to mass production of low cost sensors with advantages such as real-time detection [115], high sensitivity at low concentrations [116], portable and convenient read out circuitry [117]. Over the time researches have experimentally demonstrated various architectures of chemically sensitive FETs for sensing of multiple analytes with considerable improvement in figure of merits (FOMs) for sensors such as sensitivity, linearity, limit of detection (LOD) and signal to noise ratio (SNR) [118,119]. ...
Thesis
Full-text available
The interest in biologically sensitive feld-eﬀect transistors (BioFETs) is ﬂourishing explosively due to their potential as biosensors in biomedical, environmental monitoring, and security applications. Recently, the adoption of silicon nanowires in BioFETs has enabled the enhancement of sensing fgure of merits, and device miniaturization. However with the advent of nanoscale BioFETs, reliability issues due to difculty in controlling the fabrication parameters at nanoscale dimensions hamper the sensing performance. Recently, junctionless (JL) approach has been incorporated in feld eﬀect transistors to overcome the fabrication complexities where, current is governed by bulk conduction process. The absence of steep doping profles in JL transistors eases the fabrication complexities, reduces device variability and thermal budget. Imperatives of the performance requirements for next generation biosensors to detect the target chemical and biological molecules with higher sensitivity, small response times, and lower detection limit. However the potential of junctionless transistors as BioFETs still needs to be investigated. In the thesis we investigate diﬀerent junctionless BioFET design strategies from simulation, analytical, and fabrication perspectives. This dissertation focuses on two types of junctionless BioFETs: the ion-sensitive and dielectric modulated. First we developed the surface potential based analytical models for ion-sensitive junctionless BioFET for pH sensing applications. We propose a new simulation equivalent model for electrolyte taking into account the site binding model (SBM) where the electrolyte is considered to be a stacked structure of stern layer, ion permeable layer and bulk electrolyte. Then a poly-Si based boron in-situ doped junctionless BioFET is fabricated by generic CMOS approach and tested for pH detection. Further for the detection of weakly charged biomolecules, the design considerations of junctionless embedded cavity dielectric modulated BioFET was investigated through surface potential based analytical and simulation model. Lastly, we report a novel biosensing scheme comprising two stages (the sensing and amplifying stages) based on the gate all around dielectric modulated junctionless BioFET.
... The advancement of semiconductor technology has led to mass production of low cost sensors with advantages such as real-time detection [2], high sensitivity at low concentrations [3], portable and convenient read out circuitry [4]. sensitive FETs for sensing of multiple analytes with considerable improvement in figure of merits (FOMs) for sensors such as sensitivity, linearity, limit of detection (LOD) and signal to noise ratio (SNR) [5], [6]. Majority of biomolecule sensing experiments take place in aqueous environments in polar solvents such as water. ...
... (a) Equivalent density of states (conduction band and valence band) for 3 molar concentrations of phosphate buffer solutions in(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) pH range (b) Experimental calibration of simulation model[24]. ...
Article
Herein this paper we propose a surface potential based analytical model for planar junctionless field effect transistor (JL-FET) for pH sensing. The electrolyte considered is phosphate buffer saline (PBS) solution which has been modeled as three layered stacked structure consisting of stern layer, ion-permeable membrane and bulk electrolyte. The proposed model has been deduced considering Poisson's equation in the channel region. Relative shift in threshold voltage ( $\rm V_{Th}$ ) and maximum drain current ( $\rm I_{DS,max}$ ) have been used as sensitivity metrics. The low concentrations of electrolyte (0.01), yielded higher $\rm V_{Th}$ sensitivity of $\text{63}\;mV/pH$ and $\text{59}\;mV/pH$ for bottom and liquid gate respectively as compared to higher molar concentrations of electrolyte. For 0.01 PBS the aggregate drain current shift has been found to be $52.8\ \mu A/pH$ and is larger for liquid gate operation while as for bottom gate, shift of $18.9\ \mu A/pH$ is observed. Further considering pH range of 1-14, we computed various figure of merits (FOMs) that include sensitivity, linearity and signal to noise ratio for the device. The FOMs were computed and analyzed for independent operation of liquid and bottom gate for three different molarities of PBS (1, 0.1, 0.01) each with pH range from 1 to 14. Signal to noise ratio of drain current is found maximum for low molar concentrations of electrolyte and also is highest at point of maximum transconductance. The results obtained from analytical model are in good coherence with the TCAD simulation model.
Article
By the continuing downscaling of sub-micron transistors in the range of few to one deca-nanometers, we focus on the increasing relative level of the low-frequency noise in these devices. Large amount of published data and models are reviewed and summarized, in order to capture the state-of-the-art, and to observe that the 1/area scaling of low-frequency noise holds even for carbon nanotube devices, but the noise becomes too large in order to have fully deterministic devices with area less than 10 nm 10 nm. The low-frequency noise models are discussed from the point of view that the noise can be both intrinsic and coupled to the charge transport in the devices, which provided a coherent picture, and more interestingly, showed that the models converge each to other, despite the many issues that one can find for the physical origin of each model. Several derivations are made to explain crossovers in noise spectra, variable random telegraph amplitudes, duality between energy and distance of charge traps, behaviors and trends for figures of merit by device downscaling, practical constraints for micropower amplifiers and dependence of phase noise on the harmonics in the oscillation signal, uncertainty and techniques of averaging by noise characterization. We have also shown how the unavoidable statistical variations by fabrication is embedded in the devices as a spatial “frozen noise”, which also follows 1/area scaling law and limits the production yield, from one side, and from other side, the “frozen noise” contributes generically to temporal 1/f noise by randomly probing the embedded variations during device operation, owing to the purely statistical accumulation of variance that follows from cause-consequence principle, and irrespectively of the actual physical process. The accumulation of variance is known as statistics of “innovation variance”, which explains the nearly log-normal distributions in the values for low-frequency noise parameters gathered from different devices, bias and other conditions, thus, the origin of geometric averaging in low-frequency noise characterizations. At present, the many models generally coincide each with other, and what makes the difference, are the values, which, however, scatter prominently in nanodevices. Perhaps, one should make some changes in the approach to the low-frequency noise in electronic devices, to emphasize the “statistics behind the numbers”, because the general physical assumptions in each model always fail at some point by the device downscaling, but irrespectively of that, the statistics works, since the low-frequency noise scales consistently with the 1/area law.
Article
Field-effect transistor biosensors (Bio-FET) have attracted great interest in recent years owing to their distinctive properties like high sensitivity, good selectivity, and easy integration into portable and wearable electronic devices. Bio-FET performance mainly relies on the constituent components such as the bio-recognition layer and the transducer, which ensures device stability, sensitivity, and lifetime. Nanomaterial-based Bio-FETs are excellent candidates for biosensing applications. This review discusses the basic concepts, function, and working principles of Bio-FETs, and focuses on the progress of recent research in Bio-FETs in the sensing of neurotransmitters, glucose, nucleic acids, proteins, viruses, and cancer biomarkers using nanomaterials. Finally, challenges in the development of Bio-FETs, as well as an outlook on the prospects of nano Bio-FET-based sensing in various fields, are discussed.
Article
The high surface sensitivity of low-dimensional carbon nanomaterials renders them good candidates for noise detection. Herein, Mg-porphyrin-modified graphene field-effect transistors (FETs) were fabricated, and parts-per-billion concentrations of NO 2 were introduced to the devices. When the power spectrum density (PSD) of the Mg-porphyrin-modified graphene was measured in NO 2 , a specific PSD change near 1000 Hz was observed. This change could be due to the change in the electrical state of Mg-porphyrin caused by NO 2 adsorption. This study reveals that frequency-domain measurements of graphene FETs can be used to evaluate changes in the electronic state of molecules.
Article
As biological research has synthesized genomics, proteomics, metabolomics, and transcriptomics into systems biology, a new multiomics approach to biological research has emerged. Today, multiomics studies are challenging and expensive. An experimental platform that could unify the multiple omics approaches to measurement could increase access to multiomics data by enabling more individual labs to successfully attempt multiomics studies. Field effect biosensing based on graphene transistors have gained significant attention as a potential unifying technology for such multiomics studies. This review article highlights the outstanding performance characteristics that makes graphene field effect transistor an attractive sensing platform for a wide variety of analytes important to system biology. In addition to many studies demonstrating the biosensing capabilities of graphene field effect transistors, they are uniquely suited to address the challenges of multiomics studies by providing an integrative multiplex platform for large scale manufacturing using the well-established processes of semiconductor industry. Furthermore, the resulting digital data is readily analyzable by machine learning to derive actionable biological insight to address the challenge of data compatibility for multiomics studies. A critical stage of systems biology will be democratizing multiomics study, and the graphene field effect transistor is uniquely positioned to serve as an accessible multiomics platform.
Article
Full-text available
In small‐area transistors, the trapping/detrapping of charge carriers to/from a single trap located in the gate oxide near the Si/SiO2 interface leads to the discrete switching of the transistor drain current, known as single‐trap phenomena (STP), resulting in random telegraph signals. Utilizing the STP‐approach, liquid‐gated (LG) nanowire (NW) field‐effect transistor biosensors have recently been proposed for ultimate biosensing with enhanced sensitivity. In this study, the impact of channel doping concentration on the capture process of charge carriers by a single trap in LG silicon NW structures is investigated. A significant effect of the channel doping concentration on the single‐trap dynamic is revealed. To understand the mechanism behind unusual capture time behavior compared to that predicted by the classical Shockley–Read–Hall theory, an analytical model based on the rigorous description of the additional energy barrier that charge carriers have to overcome to be captured by the trap at different gate voltages is developed. The enhancement of the sensitivity for single‐trap phenomena biosensing with an increase of the channel doping concentration is explained within the framework of the proposed analytical model. The results open prospects for the development of advanced single trap‐based devices. Single‐trap phenomena (STP) are revealed and studied in liquid‐gated nanowire field‐effect transistors with different doping concentrations. Enhanced capture behavior is registered in the structures compared to the conventional Shockley–Read–Hall theory. Underlying mechanisms of the enhanced STP dynamic processes are explained within a proposed model and have to be considered for the development of ultrasensitive nanobiosensors utilizing STP.
Article
With the fast-shrinking of the transistor dimensions, the low-frequency noise level considerably increases emerging as an important parameter for the design of advanced devices for information technologies. Single-trap phenomena (STP) is a promising approach for the low-frequency noise suppression technique in nanotransistor biosensors by considering trapping/detrapping noise as a signal. We show a noise reduction mechanism offered by STP in nanoscale devices making the analogy with stochastic resonance effect found in biological systems by considering a single trap as a bistable stochastically driven nonlinear system which transmits and amplifies the weak signals. The STP noise suppression effect is experimentally demonstrated for the fabricated liquid-gated nanosensors exploiting STP. We found the optimal conditions and parameters including optimized gate voltages to implement a stochastic switching effect for the extraction of useful signals from the background noise level. These results should be considered for the development of reliable and highly sensitive nanoscale biosensors.