On the use of soft gamma radiation to characterize the pre-breakdown carrier multiplication in SiC power MOSFETs and its correlation to the TCR failure rate as measured by neutron irradiation

In this paper, some issues are solved that are encountered if using the high-energy gamma radiation for the non-invasive characterization of carrier multiplication in commercial, packaged SiC power devices under pre-breakdown conditions. For this scope the soft gamma emission of Am-241 (59.9 keV) is exploited, which provides higher signal generation and a more efficient collimation of the sensing beam than in the Co-60 and Cs-137 radioactive gamma sources used in a previous work. Carrier multiplication factors are measured in two different SiC power MOSFETs under different bias conditions and compared to the values obtained from the high-energy sources. Literature failure rate data for single event burnout (terrestrial cosmic radiation) as measured by neutron irradiation are correlated to the multiplication factors as measured by the Am-241 source. Finally, preliminary directions are issued to use of the multiplication factor as an indicator to define the bias derating factor for the devices under operation conditions.