Effect of power cycling tests on traps under the gate of Al_2O_3/AlGaN/GaN normally-ON devices

摘要

GaN-based power components are known to exhibit reversible instabilities in their electrical characteristics, particularly in the threshold voltage and in the on-state resistance. This is due to trap effects in the structure. Works presented in this paper attempt to answer the question of how are these traps affected during aging by power cycling and especially if there is irreversible degradation. For this purpose, power cycling tests were performed using 80 K of junction temperature swing on Normally-ON Al2O3/AlGaN/GaN MOS-HEMTs power chips reported on a direct copper bonding (DCB) substrate. The aging has been regularly interrupted in order to perform characterization of several aging indicators. Furthermore, trap characterizations, based on the analyses of transient current measurements, have been carried out during the aging process. The results show that irreversible degradation affects threshold voltage with drift to negative values for all tested samples. These drifts were mainly attributed to cumulative trapping with power cycles, probably induced by hot electrons, in a progressive and non-recoverable way.