Interplay of Surface Passivation and Electric Field in Determining ESD Behaviour of p-GaN Gated AlGaN/GaN HEMTs

In this paper, the electric field dependence of ESD robustness of p-GaN gated HEMTs is presented. The tuning parameter Al% in the bilayer AlxTi1-xO/SiO2 passivation is used to modulate the distribution of the electric field. The ESD robustness of the devices was observed to increase when the electric field intensity close to the gate edge decreased. Two distinct failure modes associated with field distribution are revealed by leakage behavior, electroluminescence microscopy and SEM imaging of ESD-damaged devices. Devices with higher electric field peaks close to the gate edge show a sudden rise in TLP leakage at snapback and are subject to gate-driven failures. Alternatively, devices with suppressed peak intensity have gradual increase in leakage after snapback, higher ESD robustness, and experience a drain to source driven failure mechanism.