This paper reports on hot electron (HE) degradation of 0.25-m Al0:25Ga0:75As/In0:2Ga0:8As/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.

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Abstruct-This letter for the first time presents results of hot electron stressing of InAlAsAnGaAsLInP high electron mobility transistors (HEMT's). High drain bias, room temperature stress cycles have been applied to 0.3 pm, SiN-passivated, latticematched devices, and the changes of the dc and rf (up to 50 GHz) characteristics have been studied. Both the dc and rf device gain degrade after stressing; the effect of the stress on the unity current gain cutoff frequency f~ is studied under different bias conditions. Results indicate that surface degradation may be responsible for the observed changes.

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