Physical Device Parameters Research Articles

Quantum coupling and self-heating impacts on threshold voltages of GaN metal–insulator-semiconductor high-electron-mobility transistors

A transient heat conduction equation has been proposed to describe the cooling process of a hot two-dimensional electron gas layer in a GaN-based transistor. This equation serves as the basis for a physical analytical model that explains the impacts of hot electrons in the hot two-dimensional electron gas layer via quantum coupling on the threshold voltage of GaN-based transistors. The temperature of the two-dimensional electron gas layer decreases to ambient temperature as time increases, and the threshold voltage shifts caused by such a temperature will recover with time. The proposed model accurately reflects the observed recovery of threshold voltage over time in experiments. At the same time, it offers insight into how the gate voltage, the source-drain voltage, and the ambient temperature can shift the threshold voltage in these transistors. The simplicity and analytic nature of this proposed model not only provide a physical origin of the threshold voltage instability in GaN-based devices but also offer the possibility for improving device reliability by selecting appropriate device physical parameters.

Addressing challenges inverse problem with convolutional neural networks and regulation techniques: Applications in extraction of physical parameters of semiconductors devices

The instability of the inverse problem is caused by its nonlocal and non-causal nature. This study addresses the inverse problem of determining the physical parameters of semiconductor devices. Based on statistical inversion theory, the probability distribution (posterior distribution) of the SBHs has been estimated by convolutional neural networks. Regularization techniques were then applied to such a distribution to accurately determine the SBHs of semiconductor devices. The results reveal that the fluctuations in the predicted SBHs by convolutional neural networks are similar to the amplitude between the upper and lower envelopes of the free decay curve. The method achieves a maximum relative error below 3.4% when using theoretical diode current–voltage data as input and maintains a relative error of less than 7% when compared to traditional methods when using experimental current–voltage data. Furthermore, the proposed method offers a mathematical interpretation of the inverse problem and demonstrates the capability of the proposed method to extract the physical parameters of semiconductor devices with a small amount of data.

Analytical Physical Model for Electrolyte Gated Organic Field Effect Transistors in the Helmholtz Approximation

AbstractThe analytical physical modeling of undoped electrolyte gated organic field effect transistors (EGOFETs) in the Helmholtz approximation is presented. A compact analytical model for the current–voltage (I–V) characteristics, which includes the effects of the access series resistance, has been derived and validated by means of 2D finite element numerical calculations. The model describes all operating regimes continuously (subthreshold, linear, and saturation regimes), covers channel lengths down to a few micrometres and only includes physical device parameters. From the model, analytical expressions have been proposed for all the phenomenological parameters (e.g., capacitance, threshold voltage, sub‐threshold slope voltage, and sub‐threshold capacitance) appearing in the commonly used ideal FET model. The derived analytical physical model provides a simple and quantitative way to analyze the electrical characteristics of EGOFETs and EGOFET biosensors beyond the use of the oversimplified and phenomenological ideal FET model.

Physical design guidelines to minimize area-specific ON-resistance for rated ON-current and breakdown voltage of GaN power HEMTs

In this article, we report on the development of an analytical model to estimate area-specific ON-state resistance (R ds,on) of GaN-based power high electron mobility transistor (HEMT) using rated device specifications—ON-state drain current (I ON) and maximum operating drain-to-source voltage (V DSO)—as input parameters. The rated I ON and V DSO are considered as fractions k and S, of the maximum possible drain current (I DS,max) and breakdown voltage (V BR), respectively, deliverable by the power device. The developed model is utilized to obtain the optimal physical design space parameters for a comb-like power HEMT design. Due consideration has been given to the trade-off between R ds,on and area-specific R ds,on of the transistor, device processing limitations for all the physical device parameters. The developed model has been validated with experimental results of prior literature. Our calculations impose a lower-bound for the best possible R ds,on as well as the area-specific on-resistance product (R ds,on AA) that can be obtained for a given starting channel sheet resistance in the comb architecture for a desired I ON − V DSO rating.

Ab initio methods for the computation of physical properties and performance parameters of electrochemical energy storage devices.

With the rapid development of electric vehicles and mobile technologies, there is a high demand for electrochemical energy storage devices and electrochemical energy conversion devices. Devices meeting these needs include metal-ion batteries (MIBs), supercapacitors (SCs), electrochromic devices (ECDs), and multifunctional devices such as electrochromic batteries and supercapatteries. Currently, the goal has been the enhancement of operational parameters and physical properties that results in a higher performance of these devices. In the case of batteries, SCs, and supercapatteries, scientists seek to improve the equilibrium voltage, energy density, power, capacitance, and charge rate. In the case of ECDs, the focus is on improvement of the optical modulation and coloration efficiency. However, synthesis and characterization of new materials, or of materials with optimized properties, is time consuming and highly expensive. Computational simulation of materials can expedite the experimental endeavor by modelling novel atomic structures and predicting device performance. This is possible using ab initio theories and applying physical principles that allow us to understand the underlying mechanisms governing the behavior of materials in these devices. Taking as a point of departure density functional theory (DFT), in this review, we discuss the first principles methods used for the computation of physical properties and performance parameters of electrochemical energy storage devices. A wide coverage of DFT is given, dealing with the strengths and weaknesses of the most popular functionals used in the field of electrochemical energy storage. With these tools, ab initio methods for the computation of basic properties such as effective mass, mobility, optical band gap, transmissivity, conductivity (ionic and electronic), and criteria for structure stability (cohesive energy, formation energy, adsorption energy, and phonon frequency) are addressed. We also highlight the first principles techniques for the calculation of performance parameters in MIBs, SCs, and ECDs.

Analytical Physical Model for Organic Metal‐Electrolyte‐Semiconductor Capacitors

AbstractThis work presents the analytical physical modeling of undoped organic metal‐electrolyte‐semiconductor (OMES) capacitors in the framework of the Nernst–Planck–Poisson theory, including the presence of compact interfacial layers. This work derives an exact analytical solution, up to a quadrature, for the stationary electric potential and charge density distributions in both the semiconductor film and the electrolyte solution, and from them the sheet semiconductor charge and the stationary differential capacitance are obtained as a function of the applied voltage. The dependence of these magnitudes on the physical device parameters, like the ionic concentration of the electrolyte, the capacitance of the interfacial compact layers and the injected hole density is then analyzed. This work shows that ionic diffusive effects in the electrolyte can play an important role in the device response, inducing a broadening of the transition from the weak to the strong accumulation regimes. This fact can make that the strong accumulation regime is not achieved in OMES within the usual voltage operation range of these devices. The analytical solution is validated by means of finite element numerical calculations. The implications of the results obtained on the physics of electrolyte gated organic field effect transistors (EGOFETs) are discussed.

Quantum coupling and hot-carriers impacts on excitons and optical spectrum of GaN devices

The tunability of optical transitions and the physical mechanism of GaN devices had been not clarified. An analytical and physical model describing how optical transitions in GaN devices depend on the source-drain voltage and the device temperature is proposed based on the three-dimensional Schrödinger equation and hot carrier effects. By comparing the shift in the peak position in the optical transitions predicted by the proposed analytical and physical model with numerical solutions to the coupled Schrödinger and Poisson equation and the shifts observed in experiments, it has been found that quantum coupling and hot carriers can a key role in such shifts. Quantum coupling and hot carriers can be a physical origin of such shifts in GaN devices. The analytical and physical model gives an analytical and simple insight into how the applied voltage and the device temperature impact the excitons and optical spectrum of GaN devices. Thus, it will benefit to optimize the physical parameters of light-emitting devices and light detectors based on GaN. • This model is based on three-dimensional Schrödinger equations. • This model gives a better physical understanding of optical transitions. • Hot carriers impact optical transitions in devices via quantum coupling. • It also offers the possibility to tune optical transitions in devices.

Robustness evaluation of electrical characteristics of sub-22 nm FinFETs affected by physical variability

The physical parameters of digital devices have been affected by process variability The paper is focused on subthreshold performance characterization of FET with Visual TCAD (Exploratory Data Analysis) tools considering the FinFET technology. So evaluating the impact of electrical characteristics in the physical variability process with the designers and Visual TCAD tools is a most crucial one. In this paper robustness evaluation of sub-22 nm FinFETs electrical characteristics affected by the physical variability process is proposed. The behaviour of a predictive data for FinFET technology, particularly for a NFET and PFET from a 20 nm technology to 7 nm technology are provided within the ON and OFF currents under the consideration of process variability effects. For a set of FinFET predictive technologies, effects of variations in process parameters on the currents of ION and IOFF are evaluated in this paper. These evaluations are help in understanding of variability sources that impact on FinFET devices and identifying of significant behavior standards with respect to the use of FinFET devices in digital designs. The results highlight that the IOFF currents are more affected by the impact of geometrical parameters on the FinFET devices than the ION currents.

Design and Parametric Analysis of GaN on Silicon High Electron Mobility Transistor for RF Performance Enhancement

The need of performance enhancement at the RF and millimeter wave is highly desirable to eliminate the heating effects and power dissipation. Silicon substarte found to be a suitable candidate which reduces about 70% channel temperature than sapphire. To achieve high performance, a GaN on the Silicon substrate high electron mobility transistor is designed and its various performance paramters are analyzed by varying the design specifications. Moreover, the problem of blocking voltage improvement is resolved by epitaxial design approach. Since, threshold voltage, doping-level, work-function of gate material and channel length are considered as some of the important parameters while device modeling. Therefore, the impact of these parameters is examined and analyzed to enehace the performance and reliability of the device for RF applications. The performance parameters like trans-conductance, drain current curves are plotted at different state of device physical and electrical parameters. Results exhibits maximum value of transconductance gm = 13 m-mho, minimum gate capacitance Cg = 0.5pf, wheras Vth is varied between − 0.25 V to 0.25 V.

Analysis of Hybrid Hetero-Homo Junction Lead-Free Perovskite Solar Cells by SCAPS Simulator

In this work, we report on the effect of substituting the active intrinsic i-layer on a conventional pin structure of lead-free perovskite solar cell (PSC) by a homo p-n junction, keeping the thickness of the active layer constant. It is expected that when the active i-layer is substituted by a p-n homo junction, one can increase the collection efficiency of the photo-generated electrons and holes due to the built-in electric field of the homo junction. The impact of the technological and physical device parameters on the performance parameters of the solar cell have been worked out. It was found that p-side thickness must be wider than the n-side, while its acceptor concentration should be slightly lower than the donor concentration of the n-side to achieve maximum efficiency. In addition, different absorber types, namely, i-absorber, n-absorber and p-absorber, are compared to the proposed pn-absorber, showing a performance-boosting effect when using the latter. Moreover, the proposed structure is made without a hole transport layer (HTL) to avoid the organic issues of the HTL materials. The back metal work function, bulk trap density and ETL material are optimized for best performance of the HTL-free structure, giving Jsc = 26.48, Voc = 0.948 V, FF = 77.20 and PCE = 19.37% for AM1.5 solar spectra. Such results highlight the prospective of the proposed structure and emphasize the importance of using HTL-free solar cells without deteriorating the efficiency. The solar cell is investigated by using SCAPS simulator.

Engineering Method for Tailoring Electrical Characteristics in TiN/TiOx/HfOx/Au Bi-Layer Oxide Memristive Devices

Memristive devices have led to an increased interest in neuromorphic systems. However, different device requirements are needed for the multitude of computation schemes used there. While linear and time-independent conductance modulation is required for machine learning, non-linear and time-dependent properties are necessary for neurobiologically realistic learning schemes. In this context, an adaptation of the resistance switching characteristic is necessary with regard to the desired application. Recently, bi-layer oxide memristive systems have proven to be a suitable device structure for this purpose, as they combine the possibility of a tailored memristive characteristic with low power consumption and uniformity of the device performance. However, this requires technological solutions that allow for precise adjustment of layer thicknesses, defect densities in the oxide layers, and suitable area sizes of the active part of the devices. For this purpose, we have investigated the bi-layer oxide system TiN/TiOx/HfOx/Au with respect to tailored I-V non-linearity, the number of resistance states, electroforming, and operating voltages. Therefore, a 4-inch full device wafer process was used. This process allows a systematic investigation, i.e., the variation of physical device parameters across the wafer as well as a statistical evaluation of the electrical properties with regard to the variability from device to device and from cycle to cycle. For the investigation, the thickness of the HfOx layer was varied between 2 and 8 nm, and the size of the active area of devices was changed between 100 and 2,500 µm2. Furthermore, the influence of the HfOx deposition condition was investigated, which influences the conduction mechanisms from a volume-based, filamentary to an interface-based resistive switching mechanism. Our experimental results are supported by numerical simulations that show the contribution of the HfOx film in the bi-layer memristive system and guide the development of a targeting device.

A Novel Approach to Model Threshold Voltage and Subthreshold Current of Graded-Doped Junctionless-Gate-All-Around (GD-JL-GAA) MOSFETs

This present article interprets the analytical models of central channel potential, the threshold voltage, and subthreshold current for Graded-Doped Junctionless-Gate-All-Around (GD-JL-GAA) MOSFETs. The parabolic approximation equation with appropriate boundary conditions has been adopted to solve the 2D Poisson’s equation for determining the central channel potential. The minimum channel potential is obtained by potential channel expression, and it is utilized to determine the threshold voltage and subthreshold current by using the Drift-Diffusion method. The behaviour of GD-JL-GAA MOSFETs has been examined by varying physical device parameters such as doping concentration (NDn), channel thickness (tsi), oxide thickness (tox), and channel length ratio (L1: L2). The mathematical analysis shows that the nominal gate leakage current in GD-JL-GAA MOSFETs due to high graded abrupt junction inside the channel region. The analytical model results have been verified with simulation data extracted from a TCAD simulator.

Modeling and optimization of an inertial triboelectric motion sensor

Abstract This paper aims to provide a better understanding of how the triboelectric effect could be utilized in the context of an inertial motion sensor. The device consists of a base-excited fixed-fixed beam carrying a middle mass that is brought into cyclic contact/separation with a dielectric mounted on the base. A theoretical model was developed encompassing both the electrical and mechanical phenomena. A low-cost device was designed and fabricated to experimentally validate the model. A parametric study was performed to distinguish the effects of the various device parameters. A hybrid Particle Swarm Optimization (PSO) and direct search technique was utilized for device improvement on some of the physical device parameters. The device was experimentally tested at input accelerations ranging from 0.4 g to 1.2 g and an objective function was formulated in terms of the output voltage density, i.e. peak output voltage per unit volume at different excitation frequencies for various design parameters. The usefulness and validity of the optimization techniques utilized was proved highlighting their possible usage in other applications based on the triboelectric effect.

Physical parameter‐based data‐driven modeling of small signal parameters of a metal‐semiconductor field‐effect transistor

AbstractIn this work, physical parameter‐based modeling of small signal parameters for a metal‐semiconductor field‐effect transistor (MESFET) has been carried out as continuous functions of drain voltage, gate voltage, frequency, and gate width. For this purpose, a device simulator has been used to generate a big dataset of which the physical device parameters included material type, doping concentration and profile, contact type, gate length, gate width, and work function. Five state‐of‐the‐art algorithms: multi‐layer perceptron (MLP), IBk, K*, Bagging, and REPTree have been used for creating a regression model. The symbolic regression algorithm has been used to obtain analytical expressions of the real and imaginary parts of the Scattering (S) parameters using the physics‐based generated dataset. The regression performances of all the benchmarks and the symbolic regression have been compared to references from the device simulator results. The results of the derived equations and the best algorithms have been then compared to the device simulator results, with case studies for validation. The DC performance characteristics of the MESFET have been also obtained. The proposed model can be used to predict the small signal parameters of new devices prior to development, and allows for both the device and circuit to be optimized for specific applications.

Analytical Modeling of Threshold Voltage for Dual-Metal Double-Gate Gate-All-Around (DM-DG-GAA) MOSFET

This paper presents, analytical modeling of surface potential,threshold voltage and DIBL for a Dual-Metal Double-Gate Gate-All-Around (DM-DG-GAA) MOSFET considering the parabolic approximation of surface potential. Poisson’s three-dimensional (3D) charge density equation has been solved by using proper boundary conditions to formulate the surface potential throughout the channel length. In this work, two gate metals of distinct work functions are used for gate electrode to create a step profile in channel potential. The potential step profile in surface potential reduces the SCEs in DM-DG-GAA MOSFET. The developed surface potential model is further considered to formulate the threshold voltage (Vth)model by using an effective conductive path and Fermi potential difference. The modeled threshold voltage is further used to find the Drain Induced Barrier Lowering (DIBL) effect. The threshold voltage and the DIBL are discussed with different values of device physical parameters like gate oxide (sio2) thickness, gate length ratio, channel thickness, and screening gate work function. This paper compares the SCEs of DM-DG-GAA MOSFET with Dual-Gate Gate-All-Around (DG-GAA) MOSFET and the results showing that DM-DG-GAA MOSFET offering better short channel characteristics than DG-GAA MOSFET. The model results are verified with simulation results generated from 3D device simulator ATLAS from SILVACO.

A parameter extraction method of the PIN diode for physics‐based circuit simulation over a wide frequency range

The accurate physical parameters of the semiconductor devices are critical to the physics-based circuit simulation, which solves the carrier transport equations to model the semiconductor devices. However, the conventional method extracts physical parameters from low-frequency measurements such as the DC I-V curve, which cannot work at high frequencies. To overcome this problem, we propose a physical parameter extraction method of the PIN diode working well from DC to microwave frequencies. Specifically, because the transit-time effects are dependent on the working frequencies and input power levels, the operation modes of the PIN diode can be divided into three cases from DC to microwave frequencies; therefore, the proposed method extracts the parameters from three measured curves, including the DC I-V curve, a small-signal, and a large-signal voltage waveform both at a microwave frequency. Experiments of a PIN diode SMP1330 circuit show that the error of the conventional method is about 45% at frequencies above 300 MHz, but the maximum error of the proposed method is only 9.5% from DC to 2 GHz. Moreover, the conventional method is unable to characterize the conductance modulation phenomenon, which leads to unexpected signal reflections in PIN limiter circuits and the missing of information in radio transceivers.

Surface Potential-Based Analytical Modeling of Electrostatic and Transport Phenomena of GaN Nanowire Junctionless MOSFET

This article presents a comprehensive analytical investigation of electrostatic and transport phenomena of GaN nanowire (NW) junctionless (JL) MOSFET. The evolution of the proposed model involves the solution of quasi 2-D Poisson equation with appropriate boundary conditions to obtain effective surface potential as a function of gate voltage. The mobile carrier density derived from the surface potential model is used to formulate the core transport model as well as to analyze the electrostatic characteristics for various physical device parameters. Short channel effect and certain nonideal effects including velocity saturation, mobility degradation, and channel length modulation have been incorporated in the core transport model. The impact of physical device parameters including channel length, NW radius, and oxide thickness on the performance metrics of the device such as subthreshold slope (SS), drain-induced barrier lowering (DIBL), and threshold voltage has been rigorously investigated. Upon analyzing the transport properties of the device, steep SS of 68 mV/dec, DIBL of 27 mV/V, and switching figure of merit <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$= {g}_{m}/\text {SS}$ </tex-math></inline-formula> ) of 0.16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$({\mu }\text {S}/{\mu }\text {m})/(\text {mV}/\text {dec})$ </tex-math></inline-formula> have been attained which makes the GaN NW JL MOSFET a promising candidate for emerging low-power application. The results of this work exhibit very good agreement with 3-D TCAD simulation and reported experimental results and thereby enhancing the reliability of the proposed model.

Extraction and Analysis of the Characteristic Parameters in Back‐to‐Back Connected Asymmetric Schottky Diode

The physical Schottky parameters of devices based on Schottky contact are important to analyze the working mechanism. This article theoretically studies the parameter characteristics of the current–voltage curve of two back‐to‐back connected Schottky contacts via the thermionic emission model, and it is found that not all the parameters are able to be extracted under some constraints. Compared with some classical extraction methods, a straightforward strategy to approach the Schottky intrinsic parameters by solving equations during the characteristic interval are presented. In addition, this method is verified on several representative standard curves and experimental curves, and the extracted parameters are highly compatible with those curves. The current extraction method will be of great significance for the design and preparation of Schottky‐based devices.

Performance investigation of steep-slope core–shell nanotube indium nitride electron–hole bilayer tunnel field effect transistor

In this paper, the effects of main physical and structural parameters on the electrical characteristics of indium nitride core–shell nanotube electron–hole bilayer tunnel field effect transistor (NEHBTFET) are comprehensively investigated via simulation study for optimizing the device performance. The proposed structure offers excellent band to band tunneling efficiency and steeper turn-on drain current by providing the tunneling junction normal to the gate electric field between the region of outer shell gate and inner core gate. The simulation results reveal that the on-state current and subthreshold swing of NEHBTFET are greatly improved via expanding the band to band tunneling area along the channel and in the vertical direction in comparison with conventional nanowire TFET with narrow lateral source–channel tunneling junction. The n+–p+ tunneling junction is created electrically in the intrinsic region and a framework of core and shell gate work function engineering are conducted via calculating 2D variation matrix of the on-state current and threshold voltage for optimizing the device performance. The sensitivity of device’s main electrical parameters with respect to the variation of device physical and geometrical parameters reveals that the electrical parameters are highly insensitive to the source doping density which solves the major challenge of low solubility of dopants in III-nitride devices. In addition, the off-state current and subthreshold swings are not affected by the gate length scaling that is an indication of feasibility of this device in nanoscale regime.

Quantum coupling and electrothermal effects on electron transport in high-electron mobility transistors

Based on the energy and momentum balance equations and three-dimensional Schrodinger equations, a physical model of the quantum coupling and electrothermal effects on the electron transport in GaN transistors is proposed. Quantum coupling and electrothermal effects in GaN transistors cause a reduction in the barrier height, changes in the quantised energy levels of the two-dimensional electron gas, and a decrease in the electron density and source–drain current. This model predicts that the current collapse in GaN transistors can occur under channel electrons with large transverse energy and it can be alleviated by optimising the physical device parameters. The gate length-dependent resistance predicted by the proposed model agrees well with the experimental data reported in the literature. Not only the physical mechanism but also the possibility to improve the reliability of high-electron mobility (HEMT) GaN transistors by optimising its physical parameters has been given in this model due to its analytic nature.