Characterization of gm-dispersion and its impact on linearity of AlGaN/GaN HEMTs for microwave applications

In this work, we present a characterization method for the characterization of g_m-dispersion and its impact on the linearity of AlGaN/GaN high-electron-mobility transistors for high-power microwave applications. The g_m-dispersion was characterized using low-frequency s-parameter measurements. We will show that there is a clear frequency dependence of the transconductance for very low frequencies. This dispersion effect furthermore directly translates into an effect on the device linearity measured by two-tone measurements which shows a frequency dependence in the same way as it was determined for the g_m-dispersion.