Christophe Charbonniaud

An Electrothermal Model for AlGaN/GaN Power HEMTs Including Trapping Effects to Improve Large-Signal Simulation Results on High VSWR

A large-signal electrothermal model for AlGaN/GaN HEMTs including gate and drain related trapping effects is proposed here. This nonlinear model is well formulated to preserve convergence capabilities and simulation times. Extensive measurements have demonstrated the impact of trapping effects on the shapes of I(V) characteristics, as well as load cycles. It is shown that accurate modeling of gate-and drain-lag effects dramatically improves the large-signal simulation results. This is particularly true when the output loads deviate from the optimum matching conditions corresponding to real-world simulations. This new model and its modeling approach are presented here. Large-signal simulation results are then reported and compared to load-pull and large-signal network analyzer measurements for several load impedances at high voltage standing wave ratio and at two frequencies.

A Drain-Lag Model for AlGaN/GaN Power HEMTs

A circuit modeling drain-lag effects has been added in a non-linear electrothermal model for AlGaN/GaN HEMTs. Modeling these trapping effects allows a better description of the I-V characteristics of measured devices as well as their large-signal characteristics. This drain-lag model is well suited to preserve the convergence capabilities and the simulation times of the non linear models of these devices. This paper presents our drain-lag modeling approach, the implementation of the model in CAD software, its operating mode, and also the parameters extraction from measurements. Then, significant comparison results will be reported on pulsed IV and large signal measurements with an AlGaN/GaN HEMT transistor.

A new nonlinear HEMT model for AlGaN/GaN switch applications

We present here a new set of equations for modeling the I-V characteristics of FETs, particularly optimized for AlGaN/GaN HEMTs. These equations describe the whole characteristics from negative to positive breakdown loci, and reproduce the current saturation at high level. Using this model allow reducing the modeling procedure duration when a same transistor topology is used for several applications in a T/R module. It can even be used for switches design, witch is the most demanding application in terms of I-V swing. Moreover, a particular care was taken to model accurately the first third orders of the current derivatives, which is important for multitone applications. There are 18 parameters for the main current source (and 6 for both diodes Igs and Igd). This can be compared to the Tajimas equations based Model [1] (13 parameters) or to the Angelov Model (14 parameters) [2], which only fit the I-V characteristics for positive values of Vds. We will detail here the model formulation, and show some measurements/modeling comparisons on both I-V and [S]-parameters obtained for a 8×75 µm GaN HEMT.

Time-domain pulsed large-signal non-linear characterization of microwave transistors

Breaking-up the limitations of VNAs for RF non-linear measurements, the LSNA allows time domain characterizations of full two-port active devices. We demonstrate here some capabilities of the LSNA for pulsed RF signals. We establish a stroboscopic mode based on 3 different sampling techniques. This approach is suitable for repetitive pulsed RF signals.

A transistor measurement setup for microwave high power amplifiers design

This paper presents our view of a powerful and versatile measurement setup dedicated to nonlinear characterization and modeling of high power transistor. Our bench with on-wafer capabilities captures time domain waveforms under passive load-pull and source-pull conditions. Moreover, harmonic load-pull and pulsed mode of I(V) and/or RF operation are available. Due to the combination of several innovative features, high power measurements up to 18 GHz and 50 Watts with a gamma load factor up to 0.85 at the probe tips are made possible.