Improved parameter extraction technique for GAN HEMT's small signal model

We have investigated the influence of the reverse transfer conductance Rgd to extract the small signal parameters of GaN high electron mobility transistors (HEMTs) at microwave frequencies. In this paper a simplified method for extracting the small-signal equivalent circuit elements of HEMTs by means of measurements of scattering parameters only is presented. We have calculated the improvement in terms of first and second order error by means of inclusion of a gate drain resistance Rgd into the model. The validity of this method was verified on a set of HEMTs having different gate widths tested on wafer at several biases.