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Buffer Traps in Fe-doped AlGaN/GaN HEMTs: Investigation of the Physical Properties Based on Pulsed and Transient Measurements
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 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: (i) increasing concentrations of Fe-doping in the buffer may induce a strong current collapse, which is related to the existence of a trap level located 0.63 eV below the conduction band energy; (ii) 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; (iii) this trap behaves as a point defect clustering around dislocations. 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.
Meneghini Matteo, Rossetto Isabella, Bisi Davide, Stocco Antonio, Chini Alessandro, Meneghesso Gaudenzio, Zanoni Enrico, Pantellini Alessio, Lanzieri Claudio
Paper for Specialistic Magazine
IEEE Transaction on Electron Devices
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