THE EFFECTS OF IONIZING-RADIATION ON COMMERCIAL POWER MOSFETS OPERATED AT CRYOGENIC TEMPERATURES

This is the first report of commercial n- and p-channel power MOSFETs exposed to ionizing radiation while operating in a cryogenic environme nt. The transistors were exposed to low energy x-rays while placed in a liquid nitrogen-cooled dewar Results demonstrate significant perform ance and survivability advantages for space-borne power MOSFETs operat ed at cryogenic temperatures. The key advantages for low-temperature o peration of power MOSFET's in an ionizing radiation environment are: ( 1) steeper subthreshold current slope before and after irradiation; (2 ) lower off-state leakage currents before and after irradiation; and ( 3) larger prerad threshold voltage for n-channel devices. The first tw o points are also beneficial for devices that are not irradiated, but the advantages are more significant in radiation environments. The thi rd point is only an advantage for commercial devices operated in radia tion environments. Results also demonstrate that commercial off-the-sh elf power MOSFETs can be used for low-temperature operation in a limit ed total dose environment (i.e., many space applications).