Abstract

In this paper, AlGaAs/InGaAs pseudomorphic HEMTs have been submitted to DC life-tests in impact ionisation regime with and without thermal stress. Control devices present an identical and steep shape of the on-state breakdown locus while aged devices present a large dispersion of this characteristic. It seems that some slight modification of the surface properties and/or micro-defects located in the gate-drain region affect the on-state breakdown voltage loci measured with a gate current of 0.13mA/mm. After the two life-tests, the temperature evolution of the surface leakage contribution to the reverse gate current has increased while impact ionisation current remains unchanged. This result is confirmed by a weak temperature dependence of the on-state breakdown voltage measured with a gate current of 1mA/mm. These slight modifications of the surface properties do not affect the reliability of this technology.