This paper presents a new modeling approach accounting for the nonlinear description of low-frequency dispersive effects (due to thermal phenomena and traps) affecting electron devices. The theoretical formulation is quite general and includes as particular cases different models proposed in the literature. A large set of experimental results, oriented to microwave GaN power amplifier design, is provided to give an exhaustive validation under realistic device operation.

Nonlinear Dispersive Modeling of Electron Devices Oriented to GaN Power Amplifier Design

In this paper, an accurate table-based large-signal model for AlGaN/GaN HEMTs accounting for trapping- and self-heating-induced current dispersion is presented. The B-spline-approximation technique is used for the model-element construction, which improves the intermodulation-distortion (IMD) simulation. The dynamic behavior of the trapping and self-heating processes is taken into account in the implementation of the model. The model validity is verified by comparing the simulated and measured outputs of the device tested under pulsed and continuous large-signal excitations for devices of 1-mm gate width. Single- and two-tone simulation results show that the model can efficiently predict the output power and its harmonics and the associated IMD under different input-power and bias conditions.

Large-Signal Model for AlGaN/GaN HEMTs Accurately Predicts Trapping- and Self-Heating-Induced Dispersion and Intermodulation Distortion

A complete empirical large-signal model for high-power AlGaN/GaN HEMTs (GaN HEMT) utilizing an improved drain current (Ids) formulation with self-heating and charge- trapping modifications is presented. The new drain current equation accurately models the asymmetric bell-shaped transconductance (gm) for high Ids over a large range of biases. A method of systematically employing dynamic IV behavior using pulsed-gate IV and pulsed-gate-pulsed-drain IV datasets over a wide variety of thermal and charge-trapping conditions is presented. The composite nonlinear model accurately predicts the dynamic IV behavior, S-parameters up to 10 GHz, and large-signal wideband harmonic behavior for a multitude of quiescent gate-source and drain-source biases as well as third-order intermodulation distortion (IM3).

A Wideband Multiharmonic Empirical Large-Signal Model for High-Power GaN HEMTs With Self-Heating and Charge-Trapping Effects

A complete solution from parameter extraction to large-signal electrothermal model generation for gallium nitride (GaN) HEMTs is presented in this paper with the consideration of trapping deduced gate and drain lag effects. The extrinsic parasitic parameters are extracted by multibias hot-FET optimization using artificial bee colony algorithm. New terminal charge ( $Q_{\mathrm {gs}}$ , $Q_{\mathrm {gd}}$ , and $Q_{\mathrm {ds}})$ models with temperature dependence are proposed to better characterize the GaN devices. Physical mechanisms of the electrothermal and trapping effects have been investigated, and the artificial neural network (ANN) is exploited to construct the drain current based on pulsed $I$ – $V$ (PIV) measurements. Besides the instantaneous terminal voltages, additional three auxiliary variables are employed to describe the memory effects of GaN HEMT: channel temperature, gate trapping state, and drain trapping state. These variables are identified from PIVs to compose the input layer of the ANN, while in the simulator, they are captured by the thermal and two envelop tracking subcircuits. These physical auxiliary variables together with the ANN technology enable unlimited fitting sets of PIVs with satisfying accuracy. Single-tone and two-tone on-wafer measurements are conducted for the verification, and a good agreement has been achieved between the measurements and simulations.

An Artificial Neural Network-Based Electrothermal Model for GaN HEMTs With Dynamic Trapping Effects Consideration

An improved large-signal modeling approach of GaN on Si devices for RF high-power applications is presented. This approach accounts for the parasitic buffer loading effect under microwave RF operation in addition to the self-heating and trap ping effects associated with high-power operation conditions. A hybrid optimization (genetic and Simplex) technique based procedure is used to determine the optimal values of the model extrinsic elements. These elements are de-embedded from multibias S-parameter measurements to find the intrinsic part of the device, which is then used to construct a nonlinear current-charge (represented by nonlinear charge and current sources) based model for the gate current of the device. Pulsed and static dc IV characteristics are used for modeling of the drain current. The validity of the developed modeling approach is verified by comparing simulated large-signal single- and two-tone simulation with measured data of a 2-mm (10 × 200 μm) GaN HEMT on Si substrate. The model has been employed for designing a class-AB power amplifier. Very good agreement between the amplifier simulation and measurement shows the validity of the model.

Improved Modeling of GaN HEMTs on Si Substrate for Design of RF Power Amplifiers

The modeling of low-frequency dispersive effects due to surface state densities, deep level traps and thermal phenomena plays an important role in the large-signal performance prediction of III-V FET's. This paper describes an empirical modeling approach to accurately predict deviations between static and dynamic drain current characteristics caused by dispersive effects in III-V devices operating at microwave frequencies. It is based on reasonable assumptions and can easily be embedded in nonlinear FET models to be used in Harmonic-Balance tools for circuit analysis and design. Experimental and simulated results, for HEMT's and GaAs MESFET's of different manufacturers, that confirm the validity of the new approach, are presented and discussed together with the characterization procedures required.

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Empirical modeling of low-frequency dispersive effects due to traps and thermal phenomena in III-V FET's

An empirical approach is proposed which accounts for low-frequency dispersive phenomena due to surface state densities, deep level traps and device heating, in the modeling of the drain current response of III-V FETs. The model, which is based on mild assumptions justified both by theoretical considerations and experimental results, has been applied to GaAs MESFETs of different manufacturers. Experimental and simulation results that confirm the validity of the model are provided in the paper. >

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Y. Newport

Papers

Empirical modeling of low-frequency dispersive effects due to traps and thermal phenomena in III-V FET's

Empirical modeling of low-frequency dispersive effects due to traps and thermal phenomena in III-V FETs