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Exploring the thermal limit of GaN power devices under extreme overload conditions

: Pribahsnik, F.P.; Nelhiebel, M.; Mataln, M.; Bernardoni, M.; Prechtl, G.; Altmann, F.; Poppitz, D.; Lindemann, A.


Microelectronics reliability 76-77 (2017), pp.304-308
ISSN: 0026-2714
Journal Article
Fraunhofer IMWS ()

The 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.