![]() ![]() In photodiodes and other detectors with some p–n or p–i–n junction, it is often caused by thermal excitation (generation) of carriers – not necessarily directly from valence to conduction band, but possibly through defect states related to crystal defects or impurities (and in that case of course with a lower activation energy). One may in principle subtract the dark current from the obtained signal either with analog electronics or with software, but that works only to a limited extent, because the dark current can be substantially temperature-dependent (see below), and it also exhibits shot noise. However, even in the absence of any light input, there is often some tiny amount of DC current, which one calls the dark current.Īn additional fluctuating current with zero mean value, caused by thermal fluctuations, is usually not called a dark current.ĭepending on the photodetector device and the conditions, the dark current can have very different magnitudes – sometimes well below 1 nA, in other cases many orders of magnitude more.įor many applications, the dark current is totally negligible, but in some cases it matters – for example, when extremely small optical powers need to be detected. Most photodetectors such as photodiodes, phototransistors, CCD sensors and phototubes produce a signal current which is more or less proportional to the incident optical power. How to cite the article suggest additional literature Definition: a current from a photodetector which occurs even in the absence of a light input
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