Hot electron degradation effects in Al/sub 0.25/Ga/sub 0.75/As/In/sub 0.2/Ga/sub 0.8/As/GaAs PHEMTs

This paper reports on hot electron stress experiments performed on 0.25 /spl mu/m AlGaAs/InGaAs/GaAs pseudomorphic HEMTs. Devices have been subjected to high drain bias stress cycles with drain voltages ranging between 5 and 8 V up to a cumulative stress time of 18 hours. The effect of the stress on the device DC characteristics is studied. In particular, stressed devices show an increase of the gate-drain breakdown voltage (breakdown walkout) and changes of the drain current in the saturation region that depend, both in magnitude and polarity, on the stress conditions: moderate stress bias and time yield an increase of the drain current, whereas more severe conditions tend to lower it.