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High-Frequency FET Modeling in GaN with Dispersion Effects
Michael Morgensen
Date: 2008-08-22
Degree: MS - Electrical Engineering
Advisory Committee
Doug Barlage - Committee ChairKevin Gard - Committee Member
Mark Johnson - Committee Member
Abstract
Techniques used to model a field-effect transistor's equivalent circuit parameters are investigated and applied to an on-wafer AlGaN/GaN HFET using high-frequency S-parameters. Analysis of a THRU line allowed substrate permittivity characterization, improving parasitic capacitance estimation. Drain-source output admittance dispersion was observed in the measured devices. This dispersion phenomena was attributed to parallel conduction and was primarily present for low drain-source bias. Dispersion complicated parameter calculation and required modification of commonly used model extraction techniques. Effective mobility was also estimated by only using information contained in the S-parameter measurements. Small-signal parameter temperature dependence was also investigated to determine each parameter's associated temperature coefficient.
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