Experimental demonstration of weibull distributed failure in p-type GaN high electron mobility transistors under high forward bias stress

This paper presents a detailed study of the failure mechanisms induced by a forward bias overstress on gallium nitride (GaN) high electron mobility transistors (HEMTs) with p-type gate. DC measurements demonstrate that GaN-HEMTs with p-GaN gate show a time-dependent catastrophic degradation when submitted to forward-gate overstress. Time to failure (TTF) can be described by a Weibull distribution and has an exponential dependence on the stress voltage. The overstress induces an increase in the gate current well correlated to the electroluminescence (EL) signal. The origin of the degradation is discussed by means of 2D simulations, suggesting that the electric field in the AlGaN has a negligible influence in the failure process.