RF small-signal and power characterization of AlGaN/GaN HEMTs

S-parameter and load pull measurements are used to characterize the properties of AlGaN/GaN HEMTs grown on sapphire or silicon substrates. From the small signal data it follows that the cut-off frequencies f/sub T/ and f/sub max/ increase with the number of fingers, i.e. with the gate width, because of reduced contribution of parasitics to the total gate capacitance. Load-pull measurement setup is described and results of the output power, gain and PAE at 7 GHz are shown.