Absolute calibration of silicon photodiodes by purely relative measurements

Abstract

Previously verified models of windowless silicon photodiodes can be used to estimate their spectral response by purely relative measurements. The spectral reflectance is found from a single measurement at one wavelength to estimate the oxide thickness, from which the full spectral reflectance is calculated. The internal quantum deficiency of the silicon detector is found by fitting a physical model to a purely relative measurement to a spectrally invariant detector. The detector model ensures correct scaling of the responsivity. This method contributes to simplification of the traceability and promises a very cost efficient realization of an accurate independent spectral response scale. We have measured the responsivity of a silicon trap detector with this method. An uncertainty less than 0.20% was observed with 95% confidence in the spectral range from 455 nm to 760 nm. The uncertainty was calculated from the observed variance in the relative spectral response measurement. The uncertainty was limited by the signal to noise ratio (SNR) in the measurements of the relative spectral response of the silicon trap detectors.