Effects of Humidity and Cleaning on the Sensitivity of Si Photodiodes

The photodiode self-calibration technique requires the application of a water drop to the surface of the photodiode to be calibrated. By adsorption of water in the silicon oxide the reflectivity and hence the sensitivity of the photodiode changes. We show that the reflectivity of the detector can be restored to its former value by cleaning with pure ethanol. Influences of the room humidity on photodiode responsivity are discussed.