Failures of ALGaAs/GaAs HEMTs induced by hot electrons

We present in this work the rapid and irreversible degradation of electrical characteristics induced by hot electrons in unpassivated AlGaAs/GaAs HEMTs. When devices are biased at high drain-source voltages carriers can reach high energies and give rise to impact ionization phenomena. Devices biased in these conditions show a decrease of drain current, an increase of parasitic drain resistance and an increase of transconductance frequency dispersion. Degradation has been found proportional to the maximum electric field in the channel. Results suggest that hot electrons generate deep levels in the access region between gate and drain contacts possibly at the interfaces between the semiconductor layers in the gate-drain region