Equivalent-circuit–based modeling of the scattering and noise parameters for multi-finger GaAs pHEMTs

This study is focused on the experimental characterization of the high‐frequency linear behavior of interdigitated gallium arsenide (GaAs) pseudo-morphic high‐electron‐mobility transistors (pHEMTs) in terms of scatteringand noise parameters. A measurement‐based model is developed by using theequivalent‐circuit representation. The values of the extrinsic bias‐independentelements are obtained by means of the“cold”approach and then subtractedfrom the scattering parameter measurements at the bias point of interest,thereby enabling calculation of the intrinsic bias‐dependent elements. Next,the extracted small‐signal equivalent circuit is expanded by assigning anequivalent noise temperature to each resistor, thus obtaining the noise model.The validity of the extracted equivalent‐based model is fully confirmed by thegood agreement between measurements and model simulations over a broadfrequency range for devices having different number of gate fingers. Inaddition, the scaling of the achieved performance versus the total gate widthis analyzed and discussed.