Identify the INCORRECT statement

Dark current in a photodiode is the small reverse leakage current that flows when the photodiode is reverse biased and there is no incident light (in complete darkness).

It is caused by the thermal generation of electron-hole pairs in the depletion region, which leads to the flow of minority carriers across the junction. It is not caused by external background radiation.

The magnitude of this current is very small, typically in the range of nanoamperes (nA) or picoamperes (pA).

Therefore, the statement that dark current is only caused by external background radiation is incorrect.

Answer: Dark current in photo diode is only caused by external background radiation.