Irradiation effects of X-rays up to 3 MGy on hydrogen-terminated diamond MOSFETs

Irradiation effects of X-rays on characteristics of hydrogen-terminated diamond MOSFETs were investigated by experimentation. Hydrogen-terminated surfaces in the bare state lost their conductivity at a total dose of 30 kGy; the sheet resistance changed from 30k omega sq- 1 to more than 19 M omega sq- 1. An alumina passivation layer on the hydrogen-terminated surfaces protects its conductivity up to total dose of 3 MGy or higher. Change characteristics by irradiation mainly appeared up to total dose of 100 kGy. The threshold voltage and sheet resistance changed respectively from 1.4 V to 3.5 V and 40 k omega sq- 1 to 16 k omega sq- 1. The threshold voltage and sheet resistance changed little in the region of total dose greater than 100 kGy. Presumably, this result derives from charge accumulation in the alumina passivation layer because of X-ray irradiation. Even at a 3 MGy total dose, the leakage current was more than six orders of magnitude lower than the designed drain current. No interdiffusion Au/Ru electrode was observed. These findings indicate that RADDFETs function to at least a total dose of 3 MGy.