Simulated space radiation effects on power MOSFETs in switching power supplies

Application of power MOSFETs in spaceborne power converters was simulated by exposing switched devices to low-dose-rate ionizing radiation. Both radiation-hardened and nonradiation-hardened devices were tested. The results were compared to those obtained at higher dose rates and with constant gate bias. The primary effects of ionizing radiation on power MOSFETs are changes in the threshold voltage and degradation of mobility. These effects result in slower switching speeds and reduced drive capability. Both threshold shift and mobility degradation were found to depend on bias conditions and dose rate. Therefore, to predict device behavior, both the radiation environment and the operating conditions must be taken into account.>