#sensor-noise Dark current is thermally generated noise that arises from the silicon / chemical lattice of the sensor. Electrons that are created independently of the light falling on the sensor get captured by the potential wells and counted as signal. The increase in signal also carries a statistical fluctuation called as dark current noise. Dark current noise is the statistical variation of each sensor's dark current specification. It is usually expressed in e–/p/s (electrons per pixel per second)
The dark current specification is an ensemble average of the entire array. Occasionally, an individual pixel may have a higher than average dark current generation. This is usually an effect that arises from the manufacturing process and such pixels are known as hot pixels.
https://www.photometrics.com/learn/imaging-topics/dark-current
https://www.princetoninstruments.com/learn/camera-fundamentals/scientific-camera-noise-sources