Time dependent dielectric breakdown in novel GaN metal-insulator-semiconductor high electron mobility transistors

Abstract

Power electronics is expanding as we automate and electrify our households and step into mainstream electric vehicles. Recently, GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) have been increasing in popularity for high voltage power electronics applications because they combine high electron mobility with low gate leakage, increasing efficiency. This comes with the tradeoff of increased reliability concerns to be addressed before the widespread commercialization of GaN MIS-HEMTs. This thesis investigates one failure mechanism found in prototype industrial GaN MIS-HEMTs: time dependent dielectric breakdown (TDDB) of the gate insulator. TDDB occurs when a high electric field causes an accumulation of defects in the gate dielectric, forming a conducting path and rendering the device unusable. This is of major concern in GaN MIS-HEMTs because of their role as switches in high voltage circuits. In this work, we develop testing methodologies to address reticle-to-reticle variations and we estimate the lifetime of novel GaN MIS-HEMTs by performing measurements at different stress levels and temperatures in the ON and OFF-states.