Effect of Photon Energy on the Response of MOS Devices

Radiation-produced flatband voltage shifts in MOS capacitors have been measured as a function of incident photon energy and applied electric fields with UV, x- and gamma-ray sources spanning the energy range 70 eV to 1.25 MeV. Special interest was directed to the energies below 20 keV where the greatest effects on the flatband voltages were expected. At 70 eV the shifts are almost as great as those observed at 1.25 MeV (60Co). For 1.49 keV incident photons the voltage shifts are less than 1/3 those observed for 60Co photons.