Targeted Heavy-Ion Radiation of Aluminum Gallium Nitride/Gallium Nitride HEMTs

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Ten aluminum gallium nitride (AlGaN)/gallium nitride (GaN) high-electron mobility transistors (HEMTs) were irradiated with 1.7 MeV germanium (Ge) ions using the Micrometer Resolution Optical, Nuclear, and Electron Microscope (Micro-ONE) system on the high-voltage engineering (HVE) 6 MV tandem accelerator at Sandia National Laboratories. Using the Micro-ONE system enabled targeting of the gate-drain gap of the transistors with the ions. In situ measurements captured degradation in the on and semi-on bias conditions after varying levels of ion fluence targeted in the gap region; no change to the off-bias condition was observed during in situ measurement. Pre- and post-irradiation output and transfer performance measurements—including threshold voltage, transconductance, drain current, and gate diode characteristics—were compared and analyzed. Changes to these performance characteristics in the on, off, and semi-on bias conditions included decreased transconductance, decreased drain current, and changes to the diode characteristics, but with no change to the threshold voltage. A delayed response between the start of the ion irradiation and an increased degradation in gate current was observed for both the on and semi-on-state bias. A delayed response between the start of ion irradiation and an increased degradation in drain current was also observed for the semi-on-state bias. Immediate degradation to the drain current during irradiation was observed in the on-state bias. These observed changes to the AlGaN/GaN HEMT device characteristics during 1.7 MeV Ge ion irradiation are correlated to similar performance degradation mechanisms observed in previous AlGaN/GaN HEMT reliability studies.


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Journal of Radiation Effects Research and Engineering