Very high-frequency small-signal equivalent circuit for short gate-length InP HEMT's

Small-signal equivalent circuit for short gate-length InP high electron-mobility transistors (HEMT's) operating at very high frequency (HF) is proposed First, the extrinsic parameters of the equivalent circuit are determined using a cold HEMT but without forward gate bias. Then the intrinsic parameters of the equivalent circuit are extracted, including the frequency dependence of some of them, A fast and accurate method based on least-squares regressions is presented to obtain the extrinsic and intrinsic parameters from measured S-parameters. The improved equivalent circuit accurately fits the S-parameters of 0.25-mu m InP HEMT's over the 500-MHz up to 40-GHz measurement bandwidth, for all gate-to-source and drain-to-source voltages.