AUTOMATED ABSOLUTE AND RELATIVE SPECTRAL LINEARITY MEASUREMENTS ON PHOTOVOLTAIC DETECTORS

The paper discusses automated spectral linearity measurements using bo th absolute and relative methods. Results of measurements on typical s ilicon and germanium photodiodes are presented. These measurements sho w the agreement between the two methods. They also illustrate some int eresting linearity properties: wavelength dependence, detector-to-dete ctor variation, current versus current-density dependence, geometrical effects, and effect of reverse bias. In particular, it is shown that some silicon and germanium detectors must be underfilled with radiatio n to avoid edge effects. These cause nonlinearities which are generall y small (1 % level) but, in certain types of thermoelectrically cooled germanium detectors, can be very large (8 % to 10 %).