Characterization of photodiodes as transfer detector standards in the 120 nm to 600 nm spectral range

Using spectrally dispersed synchrotron radiation of continuously tuneable wavelength as delivered by the ultraviolet (UV) and vacuum ultraviolet (VUV) calibration facility of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY I in Berlin, various types of silicon photodiode have been examined for their radiometric performance in the 120 nm to 600 nm spectral range. Their absolute spectral responsivity was determined with a typical relative uncertainty of 0.7 % using the synchrotron-radiation cryogenic electricalsubstitution radiometer, SYRES, as primary detector standard. Particular emphasis has been given to the study of radiation-damage effects at wavelengths below 250 nm. In addition, the reflectance of the photodiodes was measured to determine their internal quantum efficiency. Using a physical model for the internal losses, the mean energy to create an electron-hole pair in silicon was derived.