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Reverse-bias testing in AlGaN/GaN HEMTs at high (negative) gate voltage is found to induce a catastrophic increase in gate leakage current IG, with only a slight degradation of drain current ID. Electroluminescence (EL) microscopy demonstrates that leakage current injection is localized within “hot spots” at the gate edges, possibly corresponding to defects in the semiconductor material or at the metal–semiconductor interface. The density of “hot spots” increases during tests and is correlated with the increase of IG and electroluminescence intensity and with an enhancement of trapping effects such as current collapse

A long-term 3000-hour test under on-state conditions (V DS =25V, 6W/mm constant dissipated power) and off-state conditions (V DS =46V, V GS =-6V) on GaN/AlGaN/GaN HEMTs is presented. Trapping presence and hot-electrons effect are characterized by means of low-frequency techniques (lowfrequency noise measurements, transconductance frequency dispersion, gate-lag). The on-state stress shows the most important degradation. Since our measurements point out to the creation of traps in the gate-to-drain surface region during the stress, this degradation is ascribed to the effect of hotelectrons.

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