This paper presents an extensive investigation of the properties of the trap with activation energy equal to 0.6 eV, which has been demonstrated to be responsible for current collapse (CC) in AlGaN/GaN HEMTs. The study was carried out on AlGaN/GaN HEMTs with increasing concentration of iron doping in the buffer. Based on pulsed characterization and drain current transient measurements, we demonstrate that for the samples under investigation: 1) increasing concentrations of Fe-doping in the buffer may induce a strong CC, which is related to the existence of a trap level located 0.63 eV below the conduction band energy and 2) this trap is physically located in the buffer layer, and is not related to the iron atoms but—more likely—to an intrinsic defect whose concentration depends on buffer doping. Moreover, we demonstrate that this level can be filled both under OFF-state conditions (by gate-leakage current) and under ON-state operation (when hot electrons can be injected to the buffer): for these reasons, it can significantly affect the switching properties of AlGaN/GaN HEMTs

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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

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