Transient stress characterization of AlGaN/GaN HEMTs due to electrical and thermal effects

Abstract In this paper, we present finite element simulation results of the transient stress response of an AlGaN/GaN high electron mobility transistor (HEMT). The modeling technique involves a small-scale electro-thermal model coupled to a large-scale mechanics model to determine the resulting stress distribution within a device operated under radio frequency (RF) conditions. The electrical characteristics of the modeled device were compared to experimental measurements and existing simulation data from literature for validation. The results show critical regions around the gate Schottky contact undergo drastically different transient stresses during pulsed operation. Specifically, stress profiles within the AlGaN layer around the gate foot print (GFP) undergo highly tensile electro-thermal stresses while stresses within the AlGaN outside the gate connected field plate (GCFP) towards the drain contact undergo highly tensile electrical stress and compressive thermoelastic stress. It is shown AlGaN/GaN HEMTs undergo large amounts of cyclic loading during typical transient operation. Based on these findings, transient failure mechanisms may differ from those previously studied under DC operation due to large amount of cyclic loading of a device around the gate structure.

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