Bias-Dependent Conduction-Induced Bimodal Weibull Distribution of the Time-Dependent Dielectric Breakdown in GaN MIS-HEMTs

In this article, we investigated the bimodal behavior in the Weibull distribution of time to breakdown during time-dependent dielectric breakdown (TDDB) measurement in GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) with Si3N4 gate insulator. We propose that the gate leakage current is a mixture mechanism of Poole–Frenkel (PF) emission and Fower–Nordheim (FN) tunneling current. The dominant mechanism of devices could shift from PF emission to FN tunneling when the stress bias is above a certain value, which is related to the properties of traps in the gate dielectric. The evolution of the leakage mechanism with stress bias leads to the deviation of the Weibull slope from the original one at low stress bias, where PF emission is the dominant one.