Iprrdiation Damage of MOS-FETS Operating in the Common Source Mode

Thirty-three MOS-FETS were operated at various bias points under 60Co gamma irradiation up to a total dose of approximately 107 R. The n-channel depletion, n-channel enhancement, and p-channel enhancement devices were operated at constant drain voltage in the common source mode. The results demonstrate effects of lateral oxide charge distributions along the channel between source and drain terminals. A tendency for the n-channel devices to gradually turn off is observed in addition to the threshold voltage shifts previously reported. A factor of ten improvement in radiation resistance can be obtained by using optimum device types (n-channel) at gate voltages which minimize threshold voltage shift (approximately zero volts).