A Physics-Based 1-D Equivalent Circuit Model for an AlGaN/GaN HEMT

This work presents a physics-based 1-D equivalent-circuit model (ECM) for an AlGaN/GaN HEMT. For that, it starts with the thorough derivation of an analytical 1-D model from a 2-D drift-diffusion representation of the device in a technology computer-aided design (TCAD) environment. Such a 1-D model describes the potential, charge density, and current density along the 2-DEG channel to allow the computation of the corresponding distributed voltages, currents, and charges (and so, capacitances). These are obtained by discretizing the analytical 1-D model, associating a 4-node sub-circuit to each spatial cell, and deriving a longitudinal branch current and a transversal charge source from these 4-node voltages. The ECM implementation in a time-domain or frequency-domain circuit simulator is very useful for a microwave engineer to understand the device operation and thus extract valuable information for the derivation of accurate lumped ECMs, as well as enabling the relation of the device microwave performance with its internal physical structure. To test the accuracy of the proposed ECM, its current and charge predictions obtained from a commercial circuit simulator are compared with full 2-D TCAD simulations. The 1-D model was further validated by comparing its predictions with the ones obtained from TCAD simulations for different AlGaN barrier thicknesses and gate lengths.