Analysis of DC-RF Dispersion in AlGaN/GaN HFETs using RF
Waveform Engineering

Chris Roff, 1 Johannes Benedikt1 and Paul J. Tasker1
D.J. Wallis, 2 K.P. Hilton, 2 J.O. Maclean, 2 D.G. Hayes, 2 M. J. Uren1,2 and T. Martin2
1Cardiff School of Engineering, Cardiff University, Cardiff, UK. email:
2 QinetiQ Ltd., Malvern, Worcestershire, UK. WR14 3PS
Keywords: GaN, HFET, DC-RF Dispersion.

This paper describes an observed difference in how DC-RF dispersion manifests itself in AlGaN/GaN HFETs when the devices are driven into different RF load impedances. The localised nature of the dispersion on the IV plane has been observed in RF waveform measurements and is explained through physical modelling. The difference in dispersive behaviours has been attributed to the geometry of the trap induced virtual gate region and the resulting carrier velocity
saturation being overcome by punch through effects under high electric fields.
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