Low-frequency dispersion and state dependency in modem microwave III-V HEMTs

An AlGaN/GaN HEMT- and an InAlAs/InGaAs mHEMT technology, both with a gate-length of 100 nm, are investigated w.r.t. low-frequency dispersion and state dependency vs. average gate and drain voltages. Based on a comprehensive DC-CW and pulsed-RF small-signal characterization, it is shown that the GaN HEMT shows both effects, while the mHEMT is nearly free of state dependency. A new formulation of the recently proposed integral transform large-signal FET model is capable of describing both effects in pulsed-RF and even in CW load-pull operation conditions.