A New GaN HEMT Equivalent Circuit Modeling Technique Based on X-Parameters

In this paper, a new accurate small-and large-signal equivalent-circuit-based modeling technique for gallium nitride (GaN) HEMT transistors grown on silicon substrate is presented. Despite X-parameters are developed as tools for the development of black-box modeling, they are used for equivalent-circuit-based model extraction. Unlike traditional modeling that uses the small-signal data to build with an indirect manner a nonlinear model, the proposed model is extracted from X-parameter measurements directly. However, similar to the equivalent-circuit-based models discussed in the literature, the new model is subdivided into extrinsic and intrinsic parts. The extrinsic part consists of linear elements and is related to the physical layout of the transistor. The intrinsic part can be extracted with the proposed analytical de-embedding technique. The nonlinear intrinsic elements are represented by new nonlinear lumped impedances and admittances whose extraction is carried out using a newly proposed technique. This new technique uses nonlinear network parameters, various X-parameter conversion rules, and basic analysis techniques of interconnected nonlinear networks. It is accurate and more advantageous than traditional transistor modeling techniques. The modeling procedure was applied to a 10 μm × 200 μm GaN HEMT with a gate length of 0.25 μm. A very good accordance between model simulations and measurements was obtained, validating the modeling approach.