Thermally-activated failure mechanisms of 0.25 \ \mu \mathrm{m}$ RF AIGaN/GaN HEMTs submitted to long-term life tests

Reliability and failure mechanism of
$\boldsymbol{0.25 \ \mu }\mathbf{m} \mathbf{AlGaN}/\mathbf{GaN}$
HEMTs under thermal storage tests and high temperature operating life (HTOL) tests have been evaluated. Results show that, during thermal storage tests, Schottky metal interdiffusion and gate sinking took place, possibly accompanied by thermo-mechanical degradation, with an activation energy of 1.8 eVe Failure modes consisted in carrier density decrease and sheet resistance increase, positive
$\mathbf{V}_{\mathbf{T}\mathbf{H}}$
shift and
$\mathbf{I}_{\mathbf{D}\mathbf{S}\mathbf{S}}$
decrease. During HTOL tests, the degradation is mainly due to electrochemical oxidation of AlGaN, leading to on resistance increase, and I
dss
and
$\mathbf{g}_{\mathbf{m}}$
decrease, with an activation energy of 1.0 eV.