Power stability of AlGaN/GaN HFETs at 20 W/mm in the pinched-off operation mode

High power-added efficiency (PAE) (approximate to 74%) and r f-power (20 W/mm) operation of Schottky and,insulated-gate AlGaN/GaN heterostructure field-effect transistors (HFETs) is reported at 2 GHz. In the pinched-off mode of operation, the PAE increases from a value of 55% to 74% when the drain bias is changed from 35 to 60 V. While both the Schottky and the insulated HFETs show high powers and PAE values, only the insulated-gate devices are stable at 20-W/mm output powers during a 60-h continuous wave r f-stress test. Their power drop of less than 0.1 dB is much smaller than the 0.8-dB drop for identical geometry Schottky-gate HFETs. The superior stability of the insulated-gate HFETs is attributed to the low forward gate currents.