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This paper presents a generalization of the charge-based model for ultrathin junctionless double-gate (JLDG) field-effect transistors (FETs) by including quantum electron density. The analytical derivation relies on a first-order correction to the infinite quantum well. When restricting the analysis to the first and second quantized states, the free carrier charge distribution and the current in an ultrathin body JLDG FETs are in agreement with numerical TCAD simulations in all the regions of operation, i.e., from deep depletion to accumulation and from linear to saturation. [ABSTRACT FROM AUTHOR]

This paper presents a design-oriented charge-based model for dc operation of AlGaAs/GaAs and AlGaN/GaN-based high-mobility field-effect transistors. The intrinsic model is physics-based and does not introduce any empirical parameter. The central concept is based on the linear approximation of the channel charge density with respect to the surface potential, leading to explicit and continuous expressions for charges and current in all the regions of operation, including subthreshold. In addition, an effective circuit design methodology based on the pinchoff surface potential, the pinchoff voltage and the key concept of inversion coefficient (IC) is proposed, likewise for silicon MOSFET circuits. [ABSTRACT FROM AUTHOR]

This paper presents a commercial or industrial view of III–V compact models for circuit design. We contrast the requirements of III–V modeling to those of silicon. The differences in requirements are strongly rooted in the applications that III–V devices are used in the end user of III–V models and the differences in the “ecosystems” of the technologies. These differences create both challenges and opportunity for the III–V modeling community. [ABSTRACT FROM AUTHOR]

In this paper, we develop an explicit model to predict the dc electrical behavior in ultrathin surrounding gate junctionless (JL) nanowire field-effect transistors (FETs). The proposed model considers 2-D electrical and geometrical confinements of carrier charge density within few discrete subbands. Combining a parabolic approximation of the Poisson equation, the first-order perturbation theory for the Schrödinger subband energy eigen-values and the Fermi–Dirac statistics for the confined carrier density lead to an explicit solution of the dc characteristic in ultrathin JL devices. Validity of the model has been verified with technology computer-aided design simulations. The results confirm its validity for all regions of operation, i.e., from deep depletion to accumulation and from linear to saturation. This represents an essential step toward analysis of circuits based on JL nanowire devices. [ABSTRACT FROM AUTHOR]

Critically important for electronic biosensing is to reduce detection time that is necessary to sense the capture of biomolecules. The essential factors to study the detection time are the number of captured biomolecules per unit time and the sensitivity of capturing biomolecules. In this paper, we numerically study how ac electroosmosis (ACEO) improves the performance of biosensor unit comprising 400 nanowires by using a Monte Carlo simulation. Note that the number of captured biomolecules per unit time hardly increases if a depleted fluid layer hides the biosensor unit from biomolecules in electrolyte. However, the Monte Carlo simulation tells us that ACEO removes the depleted fluid layer by circulating the electrolyte. This improves the capture efficiency by 4.4 times and the detection speed by 24.8 times. Furthermore, we discuss the scaling effect of nanowires on the sensitivity. As a result, we can more improve the sensitivity if we bury nanowires in a planar oxide layer than wrapping it by an oxide film. [ABSTRACT FROM AUTHOR]

High-resolution pH measurement is important for biomedical, food, pharmaceutical industries as well as agricultural/environmental monitoring. Among the pH-meters, FET sensors (pH-FETs) offer several advantages, such as, higher sensitivity, lower cost, and smaller size. In this paper, we develop a physics-based (Verilog-A) compact model to simulate dc, quasi-static transient, small-signal, and noise performance of pH-FET sensors. The Verilog-A implementation would allow pH-FET integration with complex signal processing circuits, and prediction of the integrated performance. The model predicts that FET thermal noise dominates in subthreshold, while FET flicker noise dominates above threshold. The minimum pH resolution is dictated by an interplay of FET and electrolyte noise sources, which are in turn functions of transistor geometry and operating condition. For a given technology node, if the sensor is designed to operate in subthreshold regime, pH-FET with shorter but wider channel has better pH resolution. In contrast, for sensor designed to operate in the inversion regime, longer and wider channel is preferred. Finally, we demonstrate the utility of the Verilog-A implementation by circuit simulation of a low-power sensor interface. [ABSTRACT FROM AUTHOR]

In this paper, a new dual-pocket (DP), dielectric modulated (DM) heterostructured tunnel field-effect transistor (DM-HTFET)-based biosensor has been reported. First, the efficacy of the DP-hetero-TFET (HTFET) has been analyzed by comparing it with other existing TFET structures. Next, a comprehensive assessment of sensitivity between single-pocket (SP) and DP-DM-HTFET biosensors for pocket thickness (${T}_{\text {pocket}}$), pocket length (${L}_{\text {pocket}}$), pocket doping (${N}_{\text {pocket}}$), work function of the gate metal, molar fraction of Ge, gate oxide layer, and gate oxide layer thickness (${T}_{\text {ox}}$) was done. Hence, a nonuniform arrangement of biomolecules inside the cavity simulation has been done using ATLAS device simulation software to validate the working ability of the proposed sensor. Significant improvement in the sensitivity due to threshold voltage (ON-current) i.e., 26.78% (78.5%), 60.8% (40.4%), 56% (${2.2} \times {10}^{{2}}$ %), and 40.6% (80.68%) has been observed for the DP-DM-HTFET over SP with the variation of ${T}_{\text {pocket}}$ , ${L}_{\text {pocket}}$ , ${N}_{\text {pocket}}$ , and ${T}_{\text {ox}}$ , respectively. DP-DM-HTFET-based current mirror circuit has also been demonstrated at the end. Sensitivity evaluation discloses that the DP-DM-HTFET can be a promising candidate for CMOS-based label-free biosensing applications. [ABSTRACT FROM AUTHOR]

The design of biosystems, biosensors, and lab-on-chips is an important field of investigation since the beginning of this century. The miniaturization and the integration constraints make the design of such systems challenging, and it is no longer possible to uncouple biology (or biochemistry) from the rest of the system. The interest of extending microelectronics computer-aided design tools to multidomain systems has already been demonstrated for two decades. Today, it becomes necessary to include biology among these domains. To enable such an evolution, we demonstrate an analogy between the behavior of biochemical systems and electrical circuits. This analogy is exploited to develop a tool for the description and the simulation of biological systems with SPICE. In addition, another analogy is drawn between molecular diffusion and heat diffusion. We also rely on it to develop an innovative framework for the simulation with SPICE of reaction–diffusion problems. The interest of such an approach is illustrated in the design of a penicillin sensor. A complete model of the system, which integrates biochemistry, electrochemistry, and electronics, is obtained. This model is then simulated for a first dimensioning of the sensor. [ABSTRACT FROM AUTHOR]

The possibility of fast label-free detection of biomolecules using electronic devices has resulted in an increased focus on developing such biosensing devices and optimizing their structure for enhanced performance. One of the main factors that determine biosensor’s performance is its sensitivity. A high sensitivity in detecting biomolecules is achieved with FET-based biosensors by biasing the device in the subthreshold regime. Recent works have shown the possibility of significantly increased sensitivity in detecting biomolecules using emerging steep subthreshold slope FETs as label-free biosensors. A lower subthreshold swing, achievable with steep subthreshold slope devices, also results in a faster response time for the biosensor. The impact-ionization MOS (I-MOS) transistor can achieve very steep subthreshold slopes as it is turned ON abruptly due to the impact ionization phenomenon. In this paper, we propose an underlap I-MOS (UI-MOS) transistor sensor for the label-free detection of the charged biomolecules. The UI-MOS is a three-terminal device with an underlap in the middle of the gate electrode serving as the location for immobilization by biomolecules. The gate electrode of the UI-MOS offers the advantage of individual addressability of biosensors in a sensor array. The compatibility of the UI-MOS with the CMOS process enables monolithic integration with the measurement circuitry. Using the TCAD simulation, we demonstrate that a biosensor based on the UI-MOS is highly sensitive to the presence of charged biomolecules. The UI-MOS, when operating in the linear regime, also experiences a large threshold voltage ( VT ) shift due to the presence of biomolecules. The performance of UI-MOS is found to be less sensitive to gate-oxide thickness variations, and shows high sensitivity for a range of gate and underlap lengths. The very high sensitivity of the UI-MOS biosensor and its compatibility with the existing CMOS processes make it an exciting alternative to the conventional FET-based biosensors. [ABSTRACT FROM AUTHOR]

In this paper, an analytical model of a four-gate dielectric modulated MOSFET for label-free electrical detection of the biomolecules has been proposed. To provide a binding site for the biomolecules, the channel region of MOSFET is left open in the four-gate configuration, which is conventionally covered by the gate electrode. As a result, the electrical characteristics of the device are affected by the neutral and charged biomolecules that binds to the underlap (open) channel region. The electrostatics is developed by solving a 2-D Poisson’s equation, assuming a parabolic potential profile along the channel direction using the conformal mapping technique and subsequently the drain current model is developed. The change in the threshold voltage is used as a sensing metric for the detection of biomolecules after their immobilization in the open region. The characteristic trends are supported and verified using the ATLAS device simulation software. [ABSTRACT FROM AUTHOR]

In this paper, analytical modeling of a charge plasma-based nanogap embedded surrounding gate MOSFET biosensor for label-free biosensing has been presented and verified with extensive simulated device data. Along the channel, considering parabolic potential profile, surface potential, threshold voltage, and drain currents have been modeled. Sensitivity has been analyzed by measuring the shift in ${I} _{ \mathrm{\scriptscriptstyle ON}}/{I} _{\mathrm{\scriptscriptstyle OFF}}$ and threshold voltage when the biosensor interacts with the neutral or charged biomolecules. Less thermal budgeting scheme with simplified fabrication process flow, i.e., no ion implantation or diffusion can be achieved easily here due to new charge plasma concept. In addition, the issues related to the doping control and random dopant fluctuations have been reduced significantly to make the device immune to the process variation. Hence, the proposed device has been optimized for the enhancement in device electrostatics and sensitivity. Extensive TCAD simulations have been performed to investigate the device parameters and to verify the model data. Hence, the proposed model can be considered as an optimal model of a biosensor for the future reference. [ABSTRACT FROM AUTHOR]

In this paper, an analytical model for a p-n-p-n tunnel field-effect transistor (TFET) working as a biosensor for label-free biomolecule detection purposes is developed and verified with device simulation results. The model provides a generalized solution for the device electrostatics and electrical characteristics of the p-n-p-n-TFET-based sensor and also incorporates the two important properties possessed by a biomolecule, i.e., its dielectric constant and charge. Furthermore, the sensitivity of the TFET-based biosensor has been compared with that of a conventional FET-based counterpart in terms of threshold voltage (Vth) shift, variation in the on-current (Ion) level, and I \rm on/Ioff ratio. It has been shown that the TFET-based sensor shows a large deviation in the current level, and thus, change in Ion can also be considered as a suitable sensing parameter. Moreover, the impacts of device parameters (channel thickness and cavity length), process variability, and process-induced damage on the sensitivity of the biosensor have also been discussed. [ABSTRACT FROM PUBLISHER]

Nanoscale filament is the active area in oxygen vacancy type resistance random access memory (ReRAM), which is formed stochastically during electric test after being fabricated in a clean room. That is, the filament dimension cannot be controlled with a designed mask pattern. Here, we introduce a formula to describe the current cycle-to-cycle trajectories based on a stochastic differential equation (SDE) with microscopic structure parameters: filament dimension and oxygen vacancy concentration. Since ReRAM conduction follows hopping, the filament can be described by a random resistance network (RRN). The stochastic configuration of an RRN follows the Brownian motion, which is the key parameter in the diffusion of SDE. The formula provides a practically quantitative filament characterization method, which is verified by direct observation of the filament in actual devices. Based on the formula, we can predict ReRAM endurance with the given microscopic structure parameters. [ABSTRACT FROM AUTHOR]

The need for reliable models that take into account the nonlinear kinetics of dopants is nowadays of paramount importance, particularly with the physical dimensions of electron devices shrinking to the deep nanoscale range and the development of emerging nanoionic systems such as the memristor. In this paper, we present a novel nonlinear dopant drift model that resolves the boundary issues existing in previously reported models that can be easily adjusted to match the dynamics of distinct memristive elements. With the aid of this model, we examine switching mechanisms, current–voltage characteristics, and the collective ion transport in two terminal memristive devices, providing new insights on memristive behavior. [ABSTRACT FROM PUBLISHER]

Neuromorphic architectures are hardware systems that aim to use the principles of neural function for their basis of operation. Their goal is to harness biologically inspired concepts such as weighted connections, activation thresholds, short-and long-term potentiation, and inhibition to solve problems in distributed computation. Compared with today’s methods of emulating neural function in software on conventional von Neumann hardware, neuromorphic systems provide the promise of inherently low power and fault-tolerant operation directly implemented into hardware, for application in distributed and embedded computing tasks, where the vast scaling of today’s architectures does not provide a long-term solution. This mini review is intended for a general engineering audience not currently familiar with this exciting research area. It provides descriptions of some of the recent advances, including supercomputer and single-device implementations, approaches based on spiking and nonspiking neurons, machine learning hardware accelerators, and those utilizing memristive devices. Hardware implementations utilizing both conventional electronic materials and organic electronic materials are reviewed. [ABSTRACT FROM PUBLISHER]

A simulation method for the electrolyte–insulator–semiconductor field-effect transistor (EISFET)-type sensor is proposed based on a well-established commercialized semiconductor 3-D technology computer-aided design simulator. The proposed method relies on the fact that an electrolyte can be described using a modified intrinsic semiconductor material because of the similarity between the electrolyte and the intrinsic semiconductor. The electrical double layer of the electrolyte is characterized in the simulation using the Gouy–Chapman–Stern model. Using the proposed simulation method, we extract the Debye lengths depending on phosphate buffered saline solutions with various concentrations and demonstrate that it is possible to simulate the screening effect. Furthermore, we investigate the responses of the EISFET-type silicon nanowire pH sensor based on our simulation method, which shows good agreement with the reported Nernst limit value. [ABSTRACT FROM PUBLISHER]

Quantum corrections based on density gradient formalism, recently introduced in the 3-D Monte Carlo (MC) module of the Glasgow “atomistic” simulator, are used to simultaneously capture quantum confinement effects as well as “ab initio” ionized impurity scattering. This has allowed us to consistently study the impact of transport variability due to scattering from random discrete dopants on the on-current variability in realistic nano-CMOS transistors. Such simulations result in an increased drain current variability when compared with the drift diffusion (DD) simulation. For the first time, a method that is used to accurately transfer the increased on-current variability obtained from the “ ab initio” MC simulations to the DD simulations is subsequently presented. The MC-corrected DD simulations are used to produce the target I–V characteristics from which the statistical compact models are extracted for use in preliminary design kits at the early stage of new technology development. [ABSTRACT FROM PUBLISHER]