Linearity of InGaAs photodiodes

摘要

In radiometry or pyrometry, radiometers are often used to assign the spectral radiance or radiance temperatures of sources using ratios of signals which can differ by several decades. For performing ratios between such sources with low uncertainties, the linearity of the detectors used in the transfer radiometers needs to be characterized. The linearity of InGaAs photodiodes has been studied using the flux-addition method using a broadband infrared source with a visible-blocking filter. Using this technique, 18 InGaAs photodiodes from four different vendors were studied without spectral filtering in a broad wavelength region from 900 nm to 1700 nm with the diodes underfilled by the incident flux. The linearity of InGaAs photodiodes was determined within the range of photocurrents from 10~(-8) A to 10~(-4) A. All the InGaAs photodiodes demonstrated linearity from 10~(-7) A to 10~(-4) A within the expanded uncertainties of 0.08% (k=2). The uncertainty in the linearity measurement below 10~(-8) A is increased due to the increased noise in the photocurrent arising from the feedback resistance of the transimpedance amplifier being greater than the shunt resistance of the photodiode.