SOME EFFECTS OF LOW-POWER ULTRAVIOLET-RADIATION ON SILICON PHOTODIODES

A short-term effect of low-power ultraviolet (UV) radiation on the wid ely used Hamamatsu S1337 photodiode is investigated. Experiments show that such photodiodes exposed to 248 nm radiation exhibit a 0,6 % incr ease in responsivity at this wavelength, and a smaller increase at lon ger wavelengths. The increase is produced during the first tens of sec onds of exposure and the new value reached by the responsivity remains stable even after further irradiation. The effect strongly depends on the wavelength of the radiation but is independent of power level wit hin the measurement range of 8 mu W to 50 mu W. The surface reflectivi ty of the photodiode is not modified, indicating that radiation direct ly affects the internal quantum efficiency. It thus seems advisable to age this type of photodiode before calibration or simply to avoid any exposure to radiation below 300 nm.