Lumped equivalent circuit de-embedding of GaAs structures [PHEMT example]

RF on-wafer device measurements require the provision of probe contact pads and transmission line structures to feed the device ports. A lumped equivalent circuit of the feed structure as determined through the measurement of on-wafer dummy structures and electromagnetic simulation enables three-step device de-embedding to be performed by matrix conversion of the measured S-parameters. The technique is applied to measurements of a Filtronic 6×50 μm GaAs PHEMT to obtain pure device data for large-signal modelling. The drawbacks of using a lumped element technique for large device structures at high frequencies are highlighted.