Estimation of the Ku-band accuracy of a simplified equivalent circuit for a Schottky gate SiN/AlGaN/GaN HEMT

Abstract

Abstract We investigate the accuracy of the internal FET equivalent circuit with only one nonlinear element – the channel current generator given by the Curtice-Ettenberg model. The parameters of this simplified equivalent circuit are assigned using the 2D quasi-hydrodynamic simulations taking into account the electron velocity overshoot. Wecalculated the power-added efficiency, transducer power gain, and other amplifier parameters as functions of the maximum available power of an 18-GHz input generator by three methods: using the full 2D model for the internal FET and the large-signal equivalent circuit – complete and simplified. Comparison of these power characteristics indicates the suitability of the simplified equivalent circuit for analysis and design of Ku-band power amplifiers based on the Schottky gate AlGaN/GaN HEMT passivated with the silicon nitride layer. Since this equivalentcircuit is implemented in various commercial software packages for analysis and design of RF and microwave devices, results of the 2D quasi-hydrodynamic simulations can be used in these packages. The software of this article makes it possible to evaluate the influence of the design features of a transistor on its electrical properties already at the design stage. As an example, we give the power characteristics calculated for two values of the dielectric constant of the passivation layer (6.5 and 1); the linear interpolation and extrapolation methods allow to talk about the transistor electrical properties also at other values of the dielectric constant. We also evaluate the effect of the passivation on the avalanche multiplication of charge carriers in the semiconductor, that is, on the validity of excluding the avalanche current generator from the feedback branch of the large-signal equivalent circuit. The validity of other simplifications of the equivalent circuit is also discussed.