In this paper, a new method for the separate extraction of the temperature-dependent source ( $R_{s}$ ) and drain ( $R_{d}$ ) access resistances in gallium nitride (GaN) high electron-mobility transistors (HEMTs) by using the definition of access resistances is reported. Based on this method, the temperature-dependent access resistances (TDARs) of a $0.15~\mu \text{m}$ gate-length GaN HEMT with unequal gate-source and gate-drain distance are extracted. By integrating the extracted access resistances into a modified Angelov model, the effects of TDARs on millimeter-wave (mmW) large-signal performance of the $0.15~\mu \text{m}$ GaN HEMT at different ambient temperatures (i.e., −55 °C, 25 °C, and 85 °C) are investigated. Moreover, the influence of temperature coefficient difference between $R_{s}$ and $R_{d}$ due to the asymmetry of the device has been also revealed. The results show that the TDARs have large impact on the large-signal modeling of mmW GaN HEMTs, and the temperature coefficients of $R_{s}$ and $R_{d}$ need to be considered separately in the modeling of asymmetric GaN HEMTs. The proposed TDARs extraction method would be useful for accurate modeling of GaN HEMTs at mmW frequencies.

Temperature-Dependent Access Resistances in Large-Signal Modeling of Millimeter-Wave AlGaN/GaN HEMTs

A laboratory setup, along with a set of measurement and identification procedures, have been developed expressly for the characterization of the thermal behavior of AlGaN/GaN HEMTs, suitable for microwave high power amplifier (HPA) design. The setup allows the measurement of the drain current time-domain dynamic response to positive drain bias pulses, performed at different temperatures and different dissipated power densities. The proposed measurement conditions discriminate thermal phenomena from electrical dispersive effects for this particular technology. Both the thermal resistance and the “transient thermal resistance” are identified for a single-cell 1-mm device and for a 4-mm power-bar composed of four devices, designed to be used as the final stage of a monolithic $C$ -band HPA for pulsed radar application. Transient data allow to compute the device operative channel temperature as a function of the pulsewidth and duty cycle, which is a crucial feature for pulsed HPA applications, typical for the GaN technology. The measured thermal data point out the nonlinearity of the thermal resistance versus dissipated power and base-plate temperature and the consequent critical thermal issue inherent in physically packing together such devices.

Characterization of the Nonlinear Thermal Resistance and Pulsed Thermal Dynamic Behavior of AlGaN–GaN HEMTs on SiC

In this paper, a nonlinear modeling approach for gallium nitride high-electron mobility transistor (GaN HEMT) on Si substrate is proposed. A reliable method has been developed to extract the extrinsic elements of the model. Its main advantage is its accuracy and dependency on only pinched-off and unbiased S-parameter measurements. The extrinsic elements are de-embedded from multi-bias S-parameters to characterize the transistor intrinsic and construct a large-signal model. The validity of the developed modeling approach is verified by comparing its small-signal and large-signal (single-tone and two-tone) simulations with measured data of a 2-mm GaN HEMT on Si substrate. The model has been employed for designing a class-AB power amplifier. A very good agreement between the amplifier simulation and measurement shows the validity of the model. Copyright © 2015 John Wiley & Sons, Ltd.

Efficient modeling of GaN HEMTs for linear and nonlinear circuits design

In this paper, a large signal equivalent circuit empirical model based on Anglov model for ceramic package high power AlGaN/GaN HEMT has been proposed. A temperature-dependent drain current model, including self-heating efiect, has been presented, and good agreements are achieved between measurement results and calculated results at difierent temperatures. The nonlinear capacitance models are modeled directly by measured microwave scattering (S) parameters and multi-bias small signal equivalent circuit model (SSECM) of package device is also established based on the measurements. A power amplifler based on large size AlGaN/GaN HEMT with a total gate periphery of 36mm has been designed by using the proposed model for validation purpose, and the simulation results flt the measurement results well at difierent temperatures.

/pdf/large-signal-equivalent-circuit-model-for-package-algan-gan-40qb56zjng.pdf

Large Signal Equivalent Circuit Model for Package AlGaN/GaN HEMT

The characteristics of polarizations, including spontaneous polarization (PSP) and piezoelectric polarization (PPE) in Al0.25Ga0.75N/AlN/GaN were obtained by temperature-dependent x-ray diffraction measurements of AlN and GaN layers, and the sheet carrier density (ns) in 20-nm-thick barrier Al0.25Ga0.75N/AlN/GaN heterostructure was studied by Hall measurement at different temperatures from 300 K to 600 K. It is found that the PSP/e (∼1 × 1013 cm−2, e is the electron charge) is larger than PPE/e (∼7 × 1012 cm−2). Excluding the influence of background carrier density, the change of PSP/e with temperature is similar to that of ns, while the tendency of PPE/e is opposite. The contributions to ns change by PSP and PPE are ∼−7.3 × 1011 cm−2 and ∼1.9 × 1011 cm−2, respectively. Therefore, the total variation of PSP and PPE is ∼−5.4 × 1011 cm−2, which is close to the value ∼−5.5 × 1011 cm−2 obtained by Hall data. All these results demonstrate that the PSP is dominant in temperature-dependent properties of two-dime...

Temperature-dependent polarization characteristics in Al0.25Ga0.75N/AlN/GaN heterostructure

Self-heating has a large effect on electrical performance of RF power devices. In the past, several methods were developed to estimate the average channel temperature of FETs. Some of these are based on approximate closed form expressions. These techniques give acceptable results under limited conditions and only for specific device layouts. In this proposed work, we present an accurate method for the extraction of the thermal profile of large-size AlGaN/GaN HEMTs using both Finite Element Method (FEM) simulation and measurement techniques. The thermal investigation of the complete structure of the device permits an accurate calculation of the distributed device temperature taking into account the temperature dependence of the thermal conductivities. This analysis also helps device designers tuning physical and geometrical parameters of the structure. The thermal resistances and the thermal time constants under each finger and of the whole FET structure are calculated from static and transient FEM thermal simulations, respectively. Alternatively, the thermal time constant is also determined from drain current transient measurements. Using this procedure, we obtained detailed thermal profile for AlGaN/GaN HEMT and implemented the resulting thermal sub-circuit in the large-signal model of GaN HEMTs. The simulated static and transient I(V) characteristics of the large-signal model are in good agreement with the measured data.

Thermal Model Extraction of GaN HEMTs for Large-Signal Modeling

This work presents a measurement-based physics-oriented large-signal modeling technique for GaN HEMTs. All the model elements are derived directly from pulsed-DC measurements and bias dependent small-signal model elements. The proposed small-signal model features a 12-element extrinsic network, which allows proper modeling of the complex parasitic effects present in large gate-width devices. A reliable generally applicable extrinsic extraction algorithm is presented. It is based on pinch-off S-parameter measurements and on a scanning procedure to find the optimal capacitance distribution. Results of applying the algorithm with measured data of a GaN HEMT with gate width of 3.2-mm prove the consistency of the formulation. Successful model verification is shown under pulsed-DC, single- and two-tone operations, showing accurate predictions versus measurements of IDS, Pout, gain, harmonics and IMD products.

Large-signal modeling of large-size GaN HEMTs with a comprehensive extrinsic elements extraction algorithm

Self-heating is known to affect greatly the performance of power devices. In the past, several methods were developed to estimate the average channel temperature of FETs. Some of these methods are based on approximate closed form expressions. These techniques give acceptable results under limited conditions and only for specific device layouts. In this proposed work, we present an accurate method for the extraction of the thermal profile of large-size power AlGaN/GaN HEMTs using the FEM. The thermal investigation of the complete structure of the device permits an accurate calculation of the distributed device temperature taking into account the temperature dependence of the thermal conductivities of the different layers in the HEMT structure. This analysis also helps device designers in tuning of structure's physical and geometrical parameters. The thermal resistances under each finger and of the whole FET structure are calculated. Using this procedure, we have succeeded in estimating accurately the temperature profile of the AlGaN/GaN HEMT and implemented the resulting junction thermal resistance in a large-signal model of the HEMT. This model is implemented as a look-up table in the Advanced Design Systems Software (ADS). The simulated static I(V) characteristics of the large-signal electro-thermal model are in good agreement with the measured data.

http://ieeexplore.ieee.org/iel5/5756957/5756958/05756968.pdf

Electro-Thermal Modeling of Large-Size GaN HEMTs

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Thermal Model Extraction of GaN HEMTs for Large-Signal Modeling

Large-signal modeling of large-size GaN HEMTs with a comprehensive extrinsic elements extraction algorithm

Electro-Thermal Modeling of Large-Size GaN HEMTs