Evaluation of the nonlinearity of silicon photodiodes for ultraviolet light detection

The spectral nonlinearities of various types of Si photodiodes (PDs) in the ultraviolet (UV) region were investigated. The supralinear behaviors of two Si PDs and their wavelength dependencies were observed at selected wavelengths, and a maximum value of 3.4% was obtained at an incident wavelength of 266 nm. The supralinearity values increased so that the incident wavelength was shorter, and wavelength differences in the supralinearity values of <1% were observed at a wavelength of 266 nm-375 nm for limited photocurrent. These results were due to the absorption lengths that ranged from a few nm to tens of nm for Si at the selected incident wavelengths. The supralinearity values of <0.1% for other Si PDs were observed at the selected wavelengths in the photocurrent range of 1 nA-1 mA, and no wavelength dependence was observed. These Si PDs enable accurate optical measurement in the UV region without the nonlinearity correction of Si PDs. Further, the experimental nonlinearity in the UV region would contribute to accurate UV light detection based on Si PDs with the photocurrent range more than six orders of magnitude.