HEMT Model Research Articles

Small‐signal modeling of microwave transistors using radial basis function artificial neural network‐comparison of different methods for spread constant determined

This article presents a high-precision modeling method to build a small signal model of GaAs pseudomorphic high electron mobility transistor (pHEMT) by using a radial basis function artificial neural network (RBF ANN). Both the RBF ANN Method 1 that uniformly distributed spread constant (SC) in the given range and Method 2 that increasingly changed SC with a chosen step have been modeled in this work. Compared with the l RBF ANN Method 1, the RBF ANN method 2 can automatically obtain the optimal ANN corresponding to the SC. The RBF ANN method 2 is developed for S-parameters model and equivalent circuit parameters (ECPs) model of HEMTs. S-parameters model establishes S-parameters versus bias, temperature and frequency, while the ECPs model establishes ECPs versus bias and temperature. To validate the capability of the RBF ANN in small signal modeling of GaAs pHEMTs, measured and modeled data of S-parameters model and ECPs model of a 4 × 75 μm gate width, 0.15 μm gate length GaAs pHEMT are compared, and very good agreement is achieved up to 50 GHz. For the S-parameters model, the average error of the method 2 is improved by about 20% at the temperature of −20°C, 25°C, and 85°C. For the ECPs model, the average error of the method 2 is 80% higher than that of the method 1.

Temperature dependent analytical model for transfer characteristics of GaN HEMTs with AlxInyGazN barrier layer

We present a temperature dependent analytical model for GaN HEMT with quaternary alloy AlxInyGazN barrier layer. HEMTs are also known as Heterojunction field effect transistors (HFETs). Change in the ambient temperature of device and the self-heating effects vary its threshold voltage and performance. We compare our calculated data with the available experimental data and find that the computed outcomes agree with the experimental observations existing in literature. Thereby, validating our claim that the proposed model might find use in the simulation of quaternary alloy based AlInGaN devices for various applications.

High‐frequency noise modeling of GAN HEMT with double recessed barrier layer

AbstractA physics‐based high‐frequency noise model of AlGaN/GaN HEMT with double recessed barrier layer (DRBL) is presented. A conventional GaN HEMT model is established on TCAD and verified by measurement results. A noise model of DRBL GaN HEMT up to 40 GHz is investigated based on the established model. The results show that DRBL HEMT reduces the high frequency noise and the reduction becomes more obvious as the frequency increases. Further investigation about noise performance is studied by changing the depth and length of the recessed regions. The results show that DRBL HEMT obtains the best noise performance when the length and depth are 400 nm and 9 nm respectively and has application potential in the development of millimeter waves low noise devices.

A comparative study on the accuracy of small-signal equivalent circuit modeling for large gate periphery GaN HEMT with different source to drain length and gate width

In this paper, extrinsic and intrinsic parameters were extracted from the experimental S-parameters using 16- and 22-element small signal equivalent circuit model for large gate periphery GaN HEMT with different source to drain length and gate width over 500 MHz to 26 GHz range. The extraction using 22-element model shows good consistency to measured S-parameters and the maximum gain, stability factor, delta factor and K-factor with less percentage error than 16-element model. As the source to drain length is increasing, the accuracy of parameter extraction is enhanced for 22-element model. Specially for stability factor and K-factor the percentage error was reduced drastically (10.42%–4.74% and 8.13%–0.83% respectively). For increased number of fingers, the 22-element model shows more accuracy. Also, TCAD (Technology Computer-Aided Design) device simulations were done and transfer characteristic were calibrated with measured data. The simulated s-parameters were then calibrated with the experimental extrinsic parameters.

Model and Simulation of GaN-Based Pressure Sensors for High Temperature Applications—Part I: Physics Based Compact Modeling

In this work, physical compact modelling of Gallium Nitride High Electron Mobility Transistor (GaN HEMT) based pressure sensor for high temperature applications is presented. The model builds around device placement at arbitrary positions on circular membranes, which itself acts as a transducer between pressure and surface strain. The presented model is integrated with the compact Advanced SPICE Model for High Electron Mobility Transistors (ASM-HEMT), as the core HEMT model. In this part, the effects of internal strain, external strain and temperature on the HEMT characteristic pinch-off voltage is modelled as a function of epitaxial design (barrier design, device dimensions, substrate type and thickness). In addition, the device response to pressure as a function of position on the membrane is also modelled. The analytical equations to describe the mechanical strain situation at the wafer surface, was integrated in the compact model on basis of Finite Element Method (FEM) simulations. Lattice-related effects like thermal expansion and elastic constants degradation with temperature is also modelled, based on physical equations fitted to experimental published data. The model was verified against experimental C- V measurements and published experimental data of GaN HEMTs used as pressure sensors, with different substrates (Si, sapphire), different epitaxial design, and different sensor geometry. The presented compact model allows the simulation of GaN based pressure sensors as a part of a compact circuit simulation. The model developed here is used in Part II to propose an optimized design of temperature-insensitive GaN-based pressure sensor, for high temperature applications.

An Accurate Neural Network-Based Consistent Gate Charge Model for GaN HEMTs by Refining Intrinsic Capacitances

Neural network-based capacitance models are accurate, but some of them are not charge-conservative. In this work, a novel consistent gate charge model for GaN high electron mobility transistors is presented based on neural networks. The equivalent circuit parameters are extracted using the multiobjective gray wolf optimizer-based hybrid method, which improves the accuracy of parameter extraction. To obtain more reliable data sets for accurate neural network-based modeling, the outliers in the extracted intrinsic capacitances are automatically detected and removed using the isolation forest technique. The gate charge is obtained by integrating the capacitances with the voltages at different temperatures. A neural network is used to model the bias- and temperature-dependent gate charges, and the intrinsic capacitance formulation is obtained by taking the partial derivative of the gate charge function with respect to the voltages. The proposed model is charge-conservative and requires no transcapacitances. The large-signal model is implemented in the Advanced Design System and verified by small- and large-signal measurements. Good agreement is obtained between the measurements and simulations.

Modeling and Simulation of Ultrahigh Sensitive AlGaN/AlN/GaN HEMT-Based Hydrogen Gas Detector With Low Detection Limit

Presented through this work is a steady state analytical model of the GaN HEMT based gas detector. GaN with high chemical and thermal stability provides promises for detectors in hazardous environments. However, HEMT sensor resolution must be improved to develop high precision gas sensors for automotive and space applications. The proposed model aids in systematical study of the sensor performance and prediction of sensitivities. The linear relation of threshold voltage shift at thermal equilibrium is used in predicting the sensor response. Numerical model for the reaction rates and the electrical dipole at the adsorption sites at the surface and metal/semiconductor interface have been developed and the sensor performance is analyzed for various gas concentrations. The validation of the model has been achieved through surface and interfacial charge adsorption-based gate electrode work function, Schottky barrier, 2DEG and threshold voltage deduction using MATLAB and SILVACO ATLAS TCAD. Further the applicability of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{g}_{d}$ </tex-math></inline-formula> (channel conductance) as gas sensing metric is also presented. With high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{I}_{D}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{g}_{d}$ </tex-math></inline-formula> percentile sensitivities of 118.5% and 92 % for 10 ppm hydrogen concentration. The sensor shows capability for detection in sub-ppm levels by exhibiting a response of 0.043% for 0.01ppm (10 ppb) hydrogen concentration. The detection limit of the sensor (1% sensitivity) presented here is 169 ppb and the device current increases by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$34.2~\mu \text{A}$ </tex-math></inline-formula> for 1ppb hydrogen concentration.

On temperature‐dependent small‐signal modelling of GaN HEMTs using artificial neural networks and support vector regression

On temperature‐dependent small‐signal modelling of GaN HEMTs using artificial neural networks and support vector regression

Analysis and Suppression of High Speed Dv/Dt Induced False Turn-on in GaN HEMT Phase-Leg Topology

Gallium nitride high electron mobility transistor (GaN HEMT) is liable to gate false turn-on problem when the gate crosstalk voltage exceeds its threshold voltage in the widely adopted phase-leg topology due to its low threshold voltage and high switching speed. Without considering the gate loop stray inductance, gate internal resistance, nonlinearity of parasitic capacitances and power loop stray parameters, traditional false turn-on analytical method is insufficient to support accurate analysis. And it has been found that GaN HEMT gate-source parasitic capacitance C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> previously assumed constant is otherwise highly nonlinear and has strong impacts on the gate crosstalk voltage. This paper has measured C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> by vector network analyzer and constructed an accurate nonlinear model of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> , based on which an accurate GaN HEMT behavior model is further fulfilled. The accuracy of the proposed behavior model has been verified by large amounts of experiment results. The proposed GaN HEMT model is used to accurately calculate gate crosstalk voltage and switching losses. Besides, false turn-on induced extra loss has been calculated and is adopted as a criterion to evaluate the severity of false turn-on and optimal design method for false turn-on suppression has been detailed further.

Closed-Form Extraction Strategy of Physically Meaningful Parameters of Small-Signal HEMT Models With Distributed Parasitic Capacitive Effects

In this article, closed-form physically consistent parameter extractions are presented for small-signal models with parasitic distributed capacitive effects. First, the effective gate-source, drain-source, and gate-drain capacitances of the device are obtained and partitioned into distributed capacitive elements. With the distributed capacitive network known, a novel closed-form inductance extraction is presented, and an original series-resistance extraction is also proposed, which takes into account the distributed nature of the parasitic capacitive effects in the device model. The proposed extraction strategy has been applied to a 1.2-mm GaN HEMT and an uncertainty analysis has been performed on the basis of artificial and real S-parameters, applying the measurement uncertainty model of a commercial vector network analyzer.

An Accurate Datasheet-Based Full-Characteristics Analytical Model of GaN HEMTs for Deadtime Optimization

The gallium nitride high electron mobility transistors (GaN HEMTs) are a superior candidate for the new-generation power electronics systems with higher efficiency and power density. However, due to the unique reverse characteristics, the reverse voltage drop of GaN HEMTs is much higher than that of diode. The deadtime loss in GaN-based bridge converters will be comparable to switching losses if the deadtime is not optimized. To optimize the deadtime for higher efficiency, this article proposes an accurate analytical model of GaN HEMTs, including circuit's parasitic inductances, the nonlinear capacitances, the unique reverse characteristics, etc. Taking a GaN-based synchronous buck converter as the example, the proposed model is realized, which fully uses the datasheet to avoid additional experiments. In order to accurately measure the switching current for validation, a novel parasitics-based current measurement method is proposed. The proposed model is verified by simulation in LTspice and experiment, and good agreement is shown. Based on the accurate analytical model, the deadtime is optimized for different load currents to improve the efficiency within the full load range. Compared with the fixed deadtime of 15 ns, the increase of efficiency can be up to 8%. This work will promote the high-frequency application of GaN HEMTs.

140 W급 전력 증폭 소자의 병렬 확장형 GaN HEMT 대신호 모델

In this study, a scalable GaN HEMT large-signal model for 140-W power devices is presented. The large-signal model of an 80-finger GaN HEMT includes eight unit device models in parallel, and the large-signal model of the unit device is based on the AMCAD–FET model. The unit device includes a 10-finger GaN HEMT, a gate pad, and a drain pad. Parameters for the unit GaN HEMT model were extracted using an IVCAD program of AMCAD and a Keysight PNA-X network analyzer. The unit GaN HEMT model was verified through on-wafer load-pull measurements, and the large-signal GaN HEMT model of the large-sized 80-finger device was verified through load-pull measurements of the packaged device.

An RF Approach to Modelling Gallium Nitride Power Devices Using Parasitic Extraction

This paper begins with a comprehensive review into the existing GaN device models. Secondly, it identifies the need for a more accurate GaN switching model. A simple practical process based on radio frequency techniques using Vector Network Analyser is introduced in this paper as an original contribution. It was applied to extract the impedances of the GaN device to develop an efficient behavioural model. The switching behaviour of the model was validated using both simulation and real time double pulse test experiments at 500 V, 15 A conditions. The proposed model is much easier for power designers to handle, without the need for knowledge about the physics or geometry of the device. The proposed model for Transphorm GaN HEMT was found to be 95.2% more accurate when compared to the existing LT-Spice manufacturer model. This work additionally highlights the need to adopt established RF techniques into power electronics to reduce the learning curve while dealing with these novel high-speed switching devices.

GaN-Based Megahertz Single-Phase Inverter With a Hybrid TCM Control Method for High Efficiency and High-Power Density

Compared with traditional frequency limitation method DCM and QCFTCM for TCM-based inverter, this article proposes a hybrid TCM method, which can achieve both full range ZVS and frequency variation limitation. An accurate resonant transition model is established and the switching frequency variation range can be obtained for TCM. The hybrid control can be implemented according to the variation ratio γ. In order to determine the optimal γ, an offline optimization algorithm based on loss estimation is proposed. Therefore, an accurate analytical loss model for GaN HEMTs considering the nonlinear junction capacitance is given for TCM and hybrid TCM. The loss model shows that the total losses of hybrid TCM inverter are reduced compared with TCM. Moreover, an interleaved GaN-based megahertz single-phase inverter with digital control is demonstrated with 120 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density. The aforementioned benefits are experimentally verified in the optimal hybrid TCM. With this hybrid control, the measured peak efficiency is 98%. Compared with pure TCM mode, there is a 70% reduction in the switching frequency and the related efficiency is 0.8% higher at light loads. Higher power density (135 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) can be achieved in hybrid TCM through further increasing the switching frequency compared with pure TCM.

Large-Signal Modeling of GaN HEMTs Using Hybrid GA-ANN, PSO-SVR, and GPR-Based Approaches

This article presents an extensive study and demonstration of efficient electrothermal large-signal GaN HEMT modeling approaches based on combined techniques of Genetic Algorithm (GA) with Artificial Neural Networks (ANN), and Particle Swarm optimization (PSO) with Support Vector Regression (SVR). Another promising Gaussian Process Regression (GPR) based large-signal modeling approach is also explored and presented. The GA-ANN addresses the typical problem of local minima associated with the backpropagation (BP) based ANN. The GA successfully aids in the determination of optimal initial values for BP-ANN and enables it to find a unique optimal solution after subsequent of iterations with higher rate of convergence. This is also achieved using PSO-SVR with lower optimization variables. The developed modeling techniques are demonstrated and used to simulate the gate and drain currents of a 2-mm GaN device. All the models are relatively simple, practical, and easy to implement. The gate and drain currents models are embedded in an equivalent large-signal circuit's model and built in Advanced Design System (ADS) software. The implemented model is validated by large-signal measurements and very good fitting results have been obtained. The model also showed an accurate simulation for a nonlinear power amplifier with very good computational speed and convergence.

A Combined Broadband Model for GaN HEMTs in Admittance Domain Based on Canonical Piecewise Linear Functions

In this article, a new large-signal transistor model is proposed. The model combines the advantage of both compact modeling and behavioral modeling techniques, resulting in a new modeling methodology. The intrinsic part of the model is based on the black-box poly-harmonic distortion (PHD) framework, which is implemented using the canonical piecewise linear (CPL) functions. Thus, the new intrinsic model can cover a broad operating frequency band, across a wide range of input powers, using a compact set of model parameters. While at each fixed operating frequency and input power, the model can also accurately predict device behavior over the complete Smith chart. For the extrinsic model, the traditional extrinsic parasitic network is used, enabling access to the intrinsic device plane, as required for waveform engineering. This work examines intrinsic admittance domain models implemented using both the linear and quadratic poly-harmonic expansions. An <inline-formula> <tex-math notation="LaTeX">$8 \times 125\,\,\mu \text{m}$ </tex-math></inline-formula> GaN HEMT device with a 0.25-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> gate feature size and a commercial 10-W GaN HEMT is used during the simulation and experimental model validation. Model implementations show excellent interpolation and extrapolation capability over the frequency band across a range of input power levels in both the frequency domain and the time domain.

Consistent Surface-Potential-Based Modeling of Drain and Gate Currents in AlGaN/GaN HEMTs

In this article, the gate current in AlGaN/GaN high-electron mobility transistors is modeled in a surface potential-based compact model. The thermionic emission, the Poole–Frenkel emission, and the Fowler–Nordheim tunneling are the dominant mechanisms for the gate current in the forward- and reverse-bias regions. These conduction mechanisms are modeled within the framework of the ASM-GaN compact model, which is a physics-based industry-standard model for GaN HEMTs, hence yielding a consistent model for the drain and gate currents. The proposed model captures the gate voltage, drain voltage, temperature, and gate-length dependencies of the gate current. The results of dc gate-leakage measurements of two GaN HEMT, differing only in terms of gate length, over a wide range of temperature, showing these current-conduction mechanisms, are presented, and the proposed model is validated accordingly. The developed gate current model, implemented in Verilog-A, is in excellent agreement with the experimental data.

Modeling the Impact of the High-Field Region on the $C-V$ Characteristics in GaN HEMTs

In this article, we illustrate the impact of the high electric field region and the effects of this has on the capacitance–voltage characteristics of a GaN HEMT device. Such effects arise due to a significant spike in the electric field near the drain-side edge of the gate electrode. The presence of the high electric field has a direct impact on the intrinsic capacitances of the device. We present a physics-based compact model for the gate charge and intrinsic capacitances, which captures these effects. TCAD simulations are performed to analyze the underlying principles of such phenomena while providing validation for the proposed model. The advanced SPICE model for GaN HEMTs (ASM-GaN-HEMT) is adopted and modified to include the effects of the high electric field region. The simulation results are in excellent agreement to the TCAD and the measured data. The model is compared to simulations that neglect such effects in order to illustrate the importance of capturing the impact of high-field region on the intrinsic device capacitances.

Improved Characterization and Accurate Modelling of Drain Current Derivatives of InP Based High Electron Mobility Transistors Devices.

InP based HEMTs are of great importance, due to their enormous potential in a high-speed modern microwave circuit, power amplifier, and low noise amplifier applications. Therefore, an accurate non-linear equivalent circuit model of HEMTs is very important for an accurate circuit design. This paper presents improved characterization and accurate modelling of drain current derivatives of InP based HEMTs devices. The proposed model is simple, easy to extract, and suitable for implementation in simulation tools. The Ψ function is extended to increase the flexibility of the proposed model. A gate-drain dependent current source is added to increase the S-parameter fitting. A one-dimensional intrinsic multi-bias capacitances model is introduced to avoid convergence failure. The fitting results of the I-V characteristics and its high order derivatives show high accuracy. In addition, S-parameters and Pout for the proposed model are compared with the original Angelov model. The proposed model shows better accuracy.

A Quasi-Two-Dimensional Physics-Based Model of HEMTs without Smoothing Functions for Joining Linear and Saturation Regions of I-V Characteristics

A quasi-two-dimensional physics-based model of HEMT transistor without using any smoothing functions for joining the linear and saturation regions of current-voltage (I-V) characteristics was developed. Considering the intervalley transitions of electrons and the presence of holes in the channel of transistor, we calculated the nonuniform spatial distributions of the electrical field, electron temperature, and electron mobility within the channel. The model is in a good agreement with experimental data over the linear and saturation regions of operation. The model provides precise simulating of HEMT transistors and can be utilized as a tool for analysis and prediction of influence of the material parameters on device and circuit characteristics.