DC Reliability Study of $\text{high}-\kappa$ GaN-on-Si MOS-HEMT's for mm-Wave Power Amplifiers

We report on charge capture and emission in Metal-Oxide-Semiconductor AlGaN/AlN/GaN High-Electron Mobility Transistors (MOS-HEMT) foreseen as power amplifiers in mm-wave user-equipment operating at RF frequencies. These devices target Enhancement mode operation, necessitating the incorporation of high-permittivity
$(\mathbf{high}-\boldsymbol{\kappa})$
dielectrics to mitigate barrier thinning induced leakage. It is shown that defects in the bulk of HfO
2
or Al
2
O
3
dielectrics result in significant
$\boldsymbol{V_{t}}$
instabilities, with dielectric-dependent charge emission kinetics: band alignment between
$\mathbf{high}-\boldsymbol{\kappa}$
shallow defect levels and AlGaN conduction band enables full (Al
2
O
3
) or partial (HfO
2
) charge de-trapping, while a deeper level in HfO
2
enables trapping even at threshold conditions. The significance of this work lies in revealing the degradation modes present under DC which can also contribute at RF operating conditions.