Impact of Gamma Radiations on Static, Pulsed I–V, and RF Performance Parameters of AlGaN/GaN HEMT

In this article, the impact of gamma (
$\gamma $
) irradiation on passivated and unpassivated AlGaN/GaN HEMT is presented in detail. Passivated and unpassivated GaN-HEMT devices have been exposed to
$\gamma $
-radiations to a total dose of 10 kGy. Post-
$\gamma $
-irradiation, a refinement in ohmic contact, which makes device source/drain, is recorded. Alteration in Schottky gate electrical characteristics (
${C} - {V}$
and
${I}\!\!-\!\!{V}$
) along with advances in device drain current and transconductance has been observed in unpassivated HEMT, while it remained almost unaltered in passivated GaN-HEMT after
$\gamma $
-irradiation. The OFF-state gate leakage has deterioration in both types of HEMTs, suggesting a modification in trap concentration beneath the gate and near gate region during
$\gamma $
-exposure. This is confirmed via pulsed
${I}\!-\!{V}$
measurements. A strong upswing in drain current recovery after stress bias is recorded post-
$\gamma $
-irradiation in both types of HEMTs. This confirms that the trapping sites have been altered during
$\gamma $
-exposure. Possible reasons causing this modification are improvement in gate metal barrier inhomogeneities and reduction/rearrangement of crystal defects during
$\gamma $

-exposure
. The effect of
$\gamma $
-radiation on intrinsic/extrinsic device parameters has also been determined using S-parameters measurements. Intrinsic/extrinsic device parameters of passivated HEMT are observed to be less affected by
$\gamma $
-irradiation in comparison to unpassivated GaN-HEMT devices, and post-radiation, both the devices have similar device parameters values as it was prior radiation making it suitable for harsh environment applications.