Radiation effects on UHF power MOSFETs

The effects of ionizing radiation of UHF power MOSFETs are studied. It is found that a power MOSFET amplifier exhibits little change in output power and efficiency in the linear region, but it is seriously degraded in the saturation region. The reason for this degradation is an increase in on-resistance and a decrease in the maximum current, both caused by radiation-induced interface states. A MOSFET exposed to radiation while it is operating as an amplifier at 860 MHz has a different threshold voltage shift than one not operating at high-frequency. This phenomenon can be explained by the annealing effect of the high-frequency electric field across the gate. For improvement in radiation tolerance, a device with a thinner thermal oxide film on the offset region is proposed and discussed.<
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