A Five-Parameter Model of the AlGaN/GaN HFET

Abstract

We introduce an analytic expression for the drain current $I_{d}(V_{\rm gs},V_{\rm ds})$ of an AlGaN/GaN heterojunction field-effect transistor (HFET) as a function of its gate and drain voltages. We derive the function from a compact physical model of conduction current in the HFET. The proposed expression for the current is configured by five parameters, which can be expressed in terms of the geometry and materials of a device. We extend the model to small-signal RF operation by embedding it in a 12-parameter $RLC$ network that represents terminal feed impedances and device parasitics. We adjust the parameters of the extended model to simultaneously fit dc and RF measurements of an industrial transistor.