Temperature Dependent Characterization of GaAs MESFETs

Abstract

A procedure is described that uses precise on-wafer measurements, to extract accurate temperature dependent MESFET models. New results, presented here, explore the temperature dependence of small signal equivalent circuit parameters (ECPs) for some typical MESFET devices, and show excellent agreement between modelled and measured S-parameters for FETs and monolithic mm-wave amplifiers over temperature. A comparison to a new theoretically derived temperature model is also given. The presented work includes new results, on the temperature dependence of ECP elements for a 0.25mm × 400mm MESFET, and a 0.5mm × 300mm MESFET. Models based on these results are shown to produce an accurate prediction of temperature effects on FET, and FET based MMIC amplifier, small signal performance. The method can be employed to develop temperature dependent CAD foundry models for MESFETs. The information from these models can be used in concert with numerical and theoretical analyses to develop much needed fundamental understanding of temperature dependent FET behavior at microwave and millimeter-wave frequencies, and the physical device parameters that influence this behavior. As a step in this direction, experimentally observed ECP variations are correlated here with predictions from a newly developed theoretical temperature model for MESFETs.