This paper presents DC and AC frequency dispersion effects of the drain-source output impedance in commercially available pseudomorphic HEMTs. Inductive behaviour observed on the imaginary part of the drain-source impedance is attributed to deep traps in the GaAs substrate from DC and AC measurements versus temperature. On the other hand. DC and AC measurements indicate that kink effect signature is related to impact ionisation at the drain edge of the gate followed by trapping-detrapping processes in the substrate
