DC, low Frequency and RF drift in AlGaAs/InGaAs PM-HEMTs biased in high field and high power dissipation regime

In this work we analyze degradation phenomena observed in pseudomorphic AlGaAs/InGaAs HEMTs with Al/Ti gate metallization, which have been submitted to accelerated tests at high drain-source voltage VDS and high power dissipation PD. After these tests, we observe permanent degradation effects, consisting in electron trapping in the gate-drain access region, with consequent decrease in the longitudinal electric field and 'breakdown walkout', and in thermally-activated interdiffusion of the Al/Ti gate with decrease in the gate Schottky barrier height and increase in drain saturation current ID. Rather than causing a degradation of the rf characteristics of the device, these phenomena induce an increase in the associated rf gain at 12 GHz, the other rf characteristics being almost unchanged. Overall, the most relevant failure mode observed is an increase of low-frequency transconductance.