Identification of the intrinsic capacitive core for GaAs HEMTs by investigating the frequency behavior of the impedance parameters

The present study is focused on the analysis of the impact of the dips in the impedance parameters on the behavior of the hybrid parameters for scaled GaAs HEMTs. These dips turning into kink phenomena in the magnitude of the hybrid parameters consist of a sudden reduction of the magnitude of the impedance parameters at a given value of the frequency, due to the transition from a capacitive to an inductive behavior. A theoretical and experimental investigation is developed for determining the resonance frequency associated to such dips in terms of the equivalent circuit elements. The achieved formulas are exploited to propose a novel approach for the identification of the intrinsic capacitive core.