Characterization of the carriers' multiplication in Si and SiC power devices by soft-gamma irradiation under cryostatic conditions

The characterization of the carriers' multiplication factor is a key issue for the design of robust and reliable power semiconductor devices and for the assessment of their susceptibility to terrestrial cosmic radiation induced failures. A cryostatic setup is presented to extend the applicability of non-invasive charge spectroscopy techniques using soft-gamma radiation from an Am241 radioactive source to a broad class of Si and SiC devices. A relationship is provided to convert the multiplication factor measured at liquid nitrogen temperature to the multiplication measured at ambient temperature. A dedicated simulation scheme is proposed that couples TCAD and Monte Carlo tools to predict the spectra of the collected charge and to locate hotspots of the multiplication factor. Finally, after highlighting the correlation between the charge multiplication factor and the failure rate of power devices submitted to terrestrial cosmic radiation, the present technique is suggested as a complementary method to assess the Safe-Operating Area