Jean-Pierre Teyssier

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.

40-GHz/150-ns versatile pulsed measurement system for microwave transistor isothermal characterization

A versatile pulsed I(V) and 40-GHz RF measurement system is described with all the know-how and methods to perform efficient, safe, and reliable nonlinear transistor measurements. Capability of discrimination between thermal and trapping effects with a pulse setup is demonstrated. Capture and emission constant times of trapping effects are measured. A method to electrically measure the thermal resistance and capacitance of transistors with a pulse setup is proposed.

Fully integrated nonlinear modeling and characterization system of microwave transistors with on-wafer pulsed measurements

A novel approach for nonlinear characterization and modeling of microwave transistors has been developed. The whole process is organized as a set of methods contained in the transistor database. This implies that characterization and modeling are performed in an integrated manner. I(V) and S-parameters are measured on wafer under pulsed conditions, suitable for MESFETs, HEMTs or HBTs as illustrated by the proposed models.<<ETX>>

An improved coupling method for time domain load-pull measurements

This paper describes an efficient coupling method improving the nonlinear time domain large signal load-pull measurements of active devices. This approach consists in a small RF loop fixed near the blended line that takes place between the DUT and the tuner. We take benefit of two advantages: extremely low losses induced by the coupler, and measurements taken very close to the DUT plane. It is shown that this simple coupling solution offers an average directivity better than 15 dB (before calibration) along a wide RF band from 2 to 18 GHz. This solution is compared with the classical approach of a distributed coupler connected before and after the tuner. A LSNA calibration has been performed, it exhibits an average directivity better than 35 dB.

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.

Measurement based nonlinear electrothermal modeling of GaAs FET with dynamical trapping effects

This paper presents MESFET measurement methods based on pulsed measurements that separate trapping and thermal effects. Derived from these measurements, a model of the trapping effect is determined, as well as a thermal model. The proposed nonlinear model is validated from DC to RF frequencies, it handles dynamical dispersive effects and does not depend on the hot bias point.

Characterization and modeling of nonlinear trapping effects in power SiC MESFETs

Trapping effects in power SiC MESFETs are investigated using a pulsed I-V pulsed S-parameters measurement system. It is shown that the main effect comes from substrate (buffer) traps sensitive to the drain-source voltage. Moreover a nonlinear model of the trapping phenomenon, taking into account the electron capture and emission with different time constants allows one to predict experimentally observed I-V and RF power performances of the devices.

Introduction to measurements for power transistor characterization

In this article, we will introduce you to measurements for power transistor characterization: why they matter, why they are such a complicated, highly specialized field, and where we think the technology of power transistor characterization is headed. The characterization of microwave power transistors is an important and emerging field with many interesting engineering challenges. One can basically distinguish two areas: model extraction measurements and model validation measurements. To make things simple, isothermal pulsed-bias pulsed S-parameter measurements are typically used for model extraction purposes and load-pull measurements are typically used for model validation purposes. Both areas are rapidly evolving in order to keep track of new power transistor technology. The main issue with pulsed-bias pulsed S-parameter characterization is the need to apply pulses with ever-increasing amplitude (up to 200 V and 10 A) and ever-decreasing pulse width (smaller than 400 ns). The load-pull measurements can be done with a variety of setups, with active or passive approaches, and with or without handling harmonic frequencies. The challenges of load-pull system development are to offer time-domain voltage and current waveforms at the transistor terminals-an invaluable tool to provide insight in highly nonlinear transistor behavior-in addition to the capability to present low input impedances (1 Omega) and to handle high power levels (up to 100 W).

Pulse characterization of trapping and thermal effects of microwave GaN power FETs

An experimental characterization of GaN FETs is given in this paper. A pulsed I-V/pulsed S-parameters measurement set-up is used to investigate the trapping and thermal behavior of GaN MESFETs. It is shown that electrical performances are strongly affected by surface and substrate traps and that those effects are closely linked to the temperature of the device. RF measurements up to a drain voltage of 100 V and a temperature of 320/spl deg/C are presented.

Large-Signal Time Domain Characterization of Microwave Transistors under RF Pulsed Conditions

This paper describes a time domain measurement technique of large-signal RF pulsed waveforms, based on Agilent Nonlinear Network Measurement System (NNMS). A transistor is biased under pulsed conditions and the RF is applied during bias pulses. The paper shows how the time domain RF measurements are acquired during the pulses. Up to 12 harmonic frequencies are taken into account, in order to provide an accurate time domain voltage and current description at both transistor terminals.