1.8 MeV proton response of thermally stabilized gallium nitride RF power transistors

Abstract

Three commercially available GaN-based HEMT RF power devices were irradiated with 1.8 MeV protons in three operational modes. The operational modes were semi-on, fully-on and RF-on. The former two modes were low and manufacturer-specified quiescent levels of DC bias. The latter mode was at the manufacturer-specified quiescent DC bias with the test article under power RF operation. Thermoelectric cooling was used to minimize thermally induced parametric shifts. Electrical measurements such as ID-VG sweeps were conducted from which threshold voltage, VTH, and transconductance, gm, were calculated and plotted. RF parameters of interest were measured. S-parameter sweeps were conducted in the low power linear operational regime as well as gain measurements at a higher power level. Responses were plotted in terms of gain vs. frequency, gain vs. fluence and on Smith charts. One part type exhibited increased RF small signal gain with increasing fluence over all operational modes. The variety of responses seen indicate thorough testing of candidate devices should be performed to ensure the required level of operation for applications with high reliability requirements.