An approach to determining an equivalent circuit for HEMTs

A simple way to determine a small-signal equivalent circuit of High Electron Mobility Transistors (HEMTs) is proposed. Intrinsic elements determined by a conventional analytical parameter transformation technique are described as functions of extrinsic elements. Assuming that the equivalent circuit composed of lumped elements is valid over the whole frequency range of the measurements, the extrinsic elements are iteratively determined using the variance of the intrinsic elements as an optimization criterion. Measurements of S-parameters up to 62.5 GHz at more than 100 different bias points confirmed that the HEMT equivalent circuit is consistent for all bias points     

Analytical parameter extraction of the HBT equivalent circuit withT-like topology from measured S-parameters

A pure analytical method for extraction of the small-signal equivalent circuit parameters from measured data is presented and successfully applied to heterojunction bipolar transistors (HBT's). The T-like equivalent circuit is cut into three shells accounting for the connection, and the extrinsic and intrinsic parts of the transistor. The equivalent circuit elements are evaluated in a straightforward manner from impedance and admittance representation of the measured S-parameters. The measured data are stripped during the extraction process yielding, step by step, a full set of circuit elements without using fit methods. No additional knowledge of the transistor is needed to start the extraction process with its self-consistent iteration loop for the connection shell. The extrinsic and intrinsic equivalent circuit elements are evaluated using their bias and frequency dependencies. This method yields a deviation of less then 4% between measured and modeled S-parameters     

AlGaN/GaN高电子迁移率晶体管小信号等效电路的参数提取

本文在高电子迁移率晶体管(HEMT)小信号等效电路模型的基础上,考虑了AlGaN/GaN HEMT的结构特性,具体分析了寄生参数和本征参数的提取方法.采用这些方法,实际测量了5～10 GHz频率下HEMT器件的小信号S参数并提取了它的电学参数,S参数的计算值与实际测量值进行了比较.实验结果表明此方法简单易行,较为精确.     

Détermination rapide et précise du schéma équivalent “petit signal” des transistors à effet de champ

A new method to determine the small signal equivalent circuit of FET’s is proposed. This method consists in a direct determination of both the extrinsic and intrinsic small signal parameters in a low frequency band. This method is fast, accurate and the determined equivalent circuit fits very well the S-parameters at least up to 26.5 GHz.     

GaAsMESFET小讯号等效电路参数提取

讨论了一种提取ＧａＡｓＭＥＳＦＥＴ小讯号等效电路参数的方法，本方法可直接决定外部和本征小讯号参数。所得到的等效电路的Ｓ参数计算值与测量值基本吻合。     

A peeling algorithm for extraction of the HBT small-signal equivalent circuit

Direct extraction is the most accurate method for the determination of equivalent-circuits of heterojunction bipolar transistors (HBTs). The method is based on first determining the parasitic elements and then the intrinsic elements analytically. The accuracy and robustness of the whole algorithm therefore is determined by the quality of the extraction of the extrinsic elements. This paper focuses on a new extraction method for the extrinsic capacitances which have proven to be the main source of uncertainty compared to the other extrinsic parameters. Concerning the intrinsic parameters, all the elements are extracted using exact closed-form equations, including exact expressions for the base-collector capacitances, which model the distributed nature of the base. The expressions for the base-collector capacitances are valid for both the hybrid-/spl pi/ and the physics-based T-topology equivalent circuits. Extraction results for InP HBT devices on measured S-parameters up to 100 GHz demonstrate good modeling accuracy.     

A pure analytic method for direct extraction of collector-up HBT's small-signal parameters

A pure analytic procedure for direct extraction of the small-signal equivalent-circuit parameters, including extrinsic inductances, has been demonstrated and successfully applied to III-V and SiGe collector-up heterojunction bipolar transistors (HBTs). This method can alleviate some difficulties encountered among conventional extracting techniques that are the use of additional test structures, forward-biased measurements at specific bias conditions, and empirical optimization process. In this paper, the hybrid-/spl pi/ equivalent-circuit elements are extracted in a simple and efficient way from impedance and admittance formulation on the basis of measured S-parameters. To study the bias dependence, the extrinsic and intrinsic circuit components are evaluated under different bias conditions. The model parameters are sequentially derived during the extraction process yielding a full set of physical element values. The validity of our model is explored on pnp collector-up AlGaAs-InGaAs HBTs, and a good coincidence between measured and modeled S-parameters is observed for the entire frequency range of operation. Consistent extracted trends indicate that this improved equivalent-circuit model is suitable to be implemented in circuit simulators for microwave-circuit TCAD applications.     

Small-signal model parameter extraction of E-mode N-polar GaN MOS-HEMT using optimization algorithms and its comparison

An improved small-signal parameter extraction technique for short channel enhancement-mode N-polar GaN MOS-HEMT is proposed,which is a combination of a conventional analytical method and optimization techniques.The extrinsic parameters such as parasitic capacitance,inductance and resistance are extracted under the pinch-off condition.The intrinsic parameters of the small-signal equivalent circuit (SSEC) have been extracted including gate forward and backward conductance.Different optimization algorithms such as PSO,Quasi Newton and Firefly optimization algorithm is applied to the extracted parameters to minimize the error between modeled and measured S-parameters.The different optimized SSEC models have been validated by comparing the S-parameters and unity current-gain with TCAD simulations and available experimental data from the literature.It is observed that the Firefly algorithm based optimization approach accurately extracts the small-signal model parameters as compared to other optimization algorithm techniques with a minimum error percentage of 1.3％.     

A new empirical large-signal HEMT model

We propose an empirical large-signal model of high electron mobility transistors (HEMTs). The bias-dependent data of small-signal equivalent circuit elements are obtained from S-parameters measured at various bias settings. And C_gs, C_gd, g_m, and g_ds, are described as functions of V_gs and V_ds. We included our large-signal model in a commercially available circuit simulator as a user-defined model and designed a 30/60-GHz frequency doubler. The fabricated doubler's characteristics agreed well with the design calculations     

An investigation of the power characteristics and saturationmechanisms in HEMTs and MESFETs

A method for large-signal transistor analysis is presented. The method is based on the harmonic-balance approach but makes use of input data from measured S-parameters instead of DC or pulsed DC characteristics and a large-signal equivalent circuit with harmonic elements. The topology of this circuit is nearly identical to commonly used small-signal equivalent circuits; its application allows a detailed interpretation of the computed results, which are very precise due to the use of small-signal S-parameters. The large-signal model is applied to HEMTs and MESFETs. Their saturation mechanisms are investigated and the operational difference is discussed. The importance of including higher harmonic signal components in the large-signal analysis is also shown     

Methodology for Small-Signal Model Extraction of AlGaN HEMTs

Both large- and small-periphery AlGaN high- electron mobility transistors (HEMTs) will find applications in microwave systems from 2 to 40 GHz because of their superior power handling capability. A self-consistent approach is presented for the linear model's parameter extraction from measured S-parameters. The model for parasitics is selected to reflect loading from both the probe pads and the interconnect regions, including the air bridges. The objective is to accurately extract intrinsic model parameters as the device periphery is increased from 50 mum to 1 mm and to isolate the effects of device layouts, including air bridging the source regions. To accurately extract the shunt and series parasitics, the device must be represented in its ON- and OFF-states determined by the gate and drain bias. The intrinsic device capacitances are not negligible in the forward and beyond-pinchoff reverse bias states at zero drain bias and must be accounted for. With these corrections to the measured S-parameters, consistent results for the intrinsic device parameters are obtained with both small- and large-periphery AlGaN HEMTs.     

Fast and efficient extraction of HBT model parameters usingmultibias S-parameter sets

Accurate parameter extraction technique has been presented for a small-signal equivalent circuit model of AlGaAs-GaAs HBT's. This technique makes use of multibias data optimization regarding two sets of S-parameters in the active mode and one in the cut-off mode, under the physics-based constraint that current-dependent elements in two active bias circuits are linked to each other by the ratio of their currents. This multibias optimization as well as the constraint imposed on intrinsic parameters may reduce the degree of freedom of circuit variables and increase the probability of finding a global minimum result. As a result of this extraction, good agreement is seen between the circuit models and their measured S-parameters in the frequency range of 0.045 to 26.5 GHz     

An extraction technique for small signal intrinsic parameters of HEMTs based on artificial neural networks

This paper presents a fast and accurate procedure for extraction of small signal intrinsic parameters of AlGaAs/GaAs high electron mobility transistors (HEMTs) using artificial neural network (ANN) techniques. The extraction procedure has been done in a wide range of frequencies and biases at various temperatures. Intrinsic parameters of HEMT are acquired using its values of common-source S-parameters. Two different ANN structures have been constructed in this work to extract the parameters, multi layer perceptron (MLP) and radial basis function (RBF) neural networks. These two kinds of ANNs are compared to each other in terms of accuracy, speed and memory usage. To validate the capability of the proposed method in small signal modeling of GaAs HEMTs, data and modeled values of S-parameters of a 200 μm gate width 0.25 μm GaAs HEMT are compared to each other and very good agreement between them is achieved up to 30 GHz. The effect of bias, temperature and frequency conditions on the extracted parameters of HEMT has been investigated, and the obtained results match the theoretical expectations. The proposed model can be inserted to computer-aided design (CAD) tools in order to have an accurate and fast design, simulation and optimization of microwave circuits including GaAs HEMTs.     

A parameter extraction method using cutoff measurement for alarge-scale HSPICE model of HBT's

We present an accurate parameter extraction method for the HBT large-signal equivalent circuit model in which several extrinsic parasitics are connected to HSPICE BJT model. The measured Gummel plot are used to extract DC model parameters of HBT using HSPICE. Capacitances are then obtained from S-parameter measurements of the HBTs biased to cutoff. The other parameters are determined from the active device S-parameters. The large-signal modeled Gummel plot and S-parameters show good agreement with the measured ones, respectively     

Accurate small-signal modeling of HFET's for millimeter-waveapplications

In this paper we discuss the small-signal modeling of HFET's at millimeter-wave frequencies. A new and iterative method is used to extract the parasitic components. This method allows calculation of a π-network to model the heterojunction field-effect transistor (HFET) pads, thus extending the validity of the model to higher frequencies. Formulas are derived to translate this π-network into a transmission line. A new and general cold field-effect transistor (FET) equivalent circuit, including a Schottky series resistance, is used to extract the parasitic resistances and inductances. Finally, a new and compact set of analytical equations for calculation of the intrinsic parameters is presented. The real part of Y₁₂ is accounted for in these equations and its modeling is discussed. The accounting of Re(Y₁₂ ) improves the S-parameter modeling. Model parameters are extracted for an InAlAs/InGaAs/InP HFET from measured S-parameters up to 50 GHz, and the validity of the model is evaluated by comparison with measured data at 75-110 GHz     

Monte Carlo simulator for the design optimization of low-noiseHEMTs

A complete analysis of low-noise 0.1 μm gate AlInAs-GaInAs HEMT's has been performed by using a semiclassical Monte Carlo simulation. The validity of the model has been checked through the comparison of the simulated results with static, dynamic and noise experimental measurements of real HEMTs. In order to reproduce the experimental results, we have included in the model some important real effects such as degeneracy, surface charges, T-shape of the gate, presence of dielectrics and contact resistances. Moreover, the extrinsic parameters of the devices have been added to the usual intrinsic small-signal equivalent circuit, thus allowing the calculation of the real noise of the HEMTs (characterized using the extrinsic minimum noise figure). In this way, we make possible not only the comparison with the experimental noise results, but also the analysis of the influence of the parasitic elements, the device width or the number of gate fingers on the noise of the HEMTs. The reliability of the simulator allows us to realize “computer experiments” which will make faster and cheaper the optimization process of the device design     

A small-signal linear equivalent circuit of HEMTs fabricated onGaAs-on-Si wafers

A new small-signal linear equivalent circuit for high electron mobility transistors (HEMTs) fabricated on GaAs-on-Si wafers, HEMTs-on-Si, has been proposed. The new equivalent circuit describes the microwave characteristics of HEMTs-on-Si much better than the conventional metal-semiconductor field-effect transistor (MESFET) equivalent circuit does. Influences of the pads, the GaAs-Si interface, and the Si substrate on the microwave characteristics are included in the circuit. It also has a great advantage in that it can separately analyze the intrinsic device characteristics and influences of Si substrate and GaAs-Si interface. Analyzes using the new equivalent circuit show that the crucial problem of HEMTs-on-Si is the larger values of the pad capacitances and the drain-source capacitances than those of HEMTs fabricated on GaAs bulk wafers, HEMTs-on-GaAs, and that the substrate resistivity is not an important factor for microwave performances of HEMTs-on-Si. The microwave performance was improved by the reduction of the pad capacitances     

Nonlinear device model of microwave power GaN HEMTs for high power-amplifier design

This paper presents a nonlinear equivalent circuit model of microwave power GaN high electron-mobility transistors (HEMTs), amenable for integration into commercial harmonic balance or transient simulators. All the steps taken to extract its parameter set are explained, from the extrinsic linear elements up to the intrinsic nonlinear ones. The predictive model capabilities are illustrated with measured and simulated output power and intermodulation-distortion data of a GaN HEMT. The model is then fully validated in a real application environment by comparing experimental and simulated results of output power, power-added efficiency, and nonlinear distortion obtained from a power amplifier.     

InP high electron mobility transistors for submillimetre wave and terahertz frequency applications: A review

This paper reviews the rapid advancements being made in the development of high electron mobility transistors (HEMTs) on InP substrates for future sub-millimetre wave (30–300 GHz) and terahertz (300 GHz to 3.5 THz) frequency applications. The InP HEMTs exhibits outstanding 2-DEG properties in InAlAs/InGaAs heterostructure. This paper highlights the rapid growths in the developments of enhancement mode (E-Mode) and depletion mode (D-Mode) InP HEMTs over the last 40 years, the use of InP HEMTs for cryogenic applications, reliability issues and kink effects in InP HEMTs in detail and it also highlights the impact of geometrical dimensions and their scaling on the performance of InP HEMTs. Their uniqueness in terms of low noise, low power dissipation, high gain and high frequency of operation has fuelled the incorporation of InP HEMTs in a wide variety of applications such as high speed wireless and optical communication systems, sub-millimetre wave (S-MMW) and THz receivers and transmitters, radio astronomy and radiometry, flight communications and sensing applications, material spectroscopy, active and passive imaging applications, biomedical instrumentation applications and high speed ICs such as low noise amplifiers (LNAs), multiplier chains, switches, multiplexers and flip-flops.     

Harmonic and two-tone intermodulation distortion analyses of theinverted InGa/InAlAs/InP HBT

Harmonic and two-tone intermodulation distortion analyses of the InGaAs/InAlAs/InP collector-up heterojunction bipolar transistor (HBT) are performed by a simple Ebers-Moll model. The parasitic elements of the equivalent circuit are extracted at zero bias by numerical optimization. A semianalytical approach is used to extract the intrinsic parameters of the small-signal equivalent circuit at nonzero bias points. Appropriate equations given by device physics are fitted to the bias variation of intrinsic parameters so that the Ebers-Moll model parameters can be extracted. Agreement between simulation and measurement of harmonic and intermodulation distortion is achieved