SPECTRAL REFLECTANCE OF SILICON PHOTODIODES

A precision spectrometer was used to measure the spectral reflectance of a silicon photodiode over the wavelength range from 250 to 850 nm. The results were compared with the corresponding values predicted by a model based on thin-film Fresnel formulas and the known refractive in dices of silicon and silicon dioxide. The good agreement at the level of 2 x 10(-3) in the visible wavelength range verifies that the reflec tion model can be used for accurate extrapolation of the spectral refl ectance and responsivity of silicon photodiode devices. In addition, c haracterization of the photodiode reflectance in the ultraviolet regio n improves the accuracy of the spectral irradiance measurements when f ilter radiometers based on trap detectors are used. (C) 1998 Optical S ociety of America.