Hot electron degradation of the DC and RF characteristics of AlGaAs/InGaAs/GaAs PHEMT's

This paper reports on hot electron (HE) degradation of 0.25-/spl mu/m Al/sub 0.25/Ga/sub 0.75/As/In/sub 0.2/Ga/sub 0.8/As/GaAs PHEMT's by showing the effects of the hot electron stress on both the dc and rf characteristics. The changes of dc and rf behavior after stress turn out to be strongly correlated. Both can be attributed to a decrease of the threshold voltage yielding different effects on the device gain depending on the bias point chosen for device operation and on the bias circuit adopted: a fixed current bias scheme will minimize the changes induced by the stress. The work also presents a study of the dependence of device degradation on the stress bias condition.