Combined Effects of Radio Frequency and Gamma Irradiation on P-Channel Mosfets

The purpose of this research was to investigate the combined effects of continuous gigahertz radio frequency signals and gamma irradiation on the threshold voltage of metal oxide semiconductor field effect transistors. The Fairchild NDS352AP, a commonly used commercial device, was irradiated by a cobalt-60 source under a +5 V bias with and without a radio frequency signal applied to the gate. The threshold voltage was measured during and after irradiation. During irradiation all devices exhibited an expected negative threshold voltage shift. The application of radio frequency to the gate resulted in a 7.2% increase in the rate of change of the threshold voltage during irradiation. When RF was applied after irradiation it produced no observable change when compared to the results of samples exposed to gamma radiation alone. Few conclusions can be drawn about the effects of radio frequency on post irradiation samples owing to the long recovery time of the samples. Before irradiation the radio frequency demonstrated a 5.95% increase drain current for a given drain to source voltage during I-V measurements. The threshold voltage also increased by 1.57%. The power of the radio frequency signal was adjusted from 1 to 14 dBm with no measurable effect.