Pribahsnik, F.P.F.P.PribahsnikNelhiebel, M.M.NelhiebelMataln, M.M.MatalnBernardoni, M.M.BernardoniPrechtl, G.G.PrechtlAltmann, F.F.AltmannPoppitz, D.D.PoppitzLindemann, A.A.Lindemann2022-03-052022-03-052017https://publica.fraunhofer.de/handle/publica/25365210.1016/j.microrel.2017.07.046The performance of normally-off Gallium-Nitride (GaN) High-Electron-Mobility-Transistors (HEMTs) under extended short circuit operation is investigated. A thermal limit is found in the aluminium metallization, where at temperatures around 600°C a protrusion of the gate metal through the Inter-Level Dielectric (ILD) may form, short-circuiting gate and source metallization and thus resulting in a permanently-off failure state. The present work shows how this particular failure mode can be induced by extreme overload operation, and presents a Finite Element (FE) model which agrees with the experimental observations and gives insights in the mechanical stress-state developing in the device. The deeper thermo-mechanical understanding of the degradation mechanism suggests directions in order to improve the device's robustness.en621journal article