Question

In a photodiode, light produces

• A. Reverse current
• B. Forward current
• C. Electro - luminescence
• D. Dark current

Hint:

Photodiodes are used as light detectors and are operated in reverse bias mode.
Incident photons generate electron-hole pairs in or near the depletion region.
These carriers are swept by the reverse bias field, creating a photocurrent (which is a reverse current).
Dark current is the reverse current in the absence of light. Photocurrent adds to the dark current.

Answer 1

The Correct Option is A

A photodiode is a semiconductor p-n junction device designed to detect light. It is typically operated under reverse bias conditions. When light of sufficient energy (greater than the bandgap energy of the semiconductor) strikes the depletion region of the reverse-biased photodiode, it generates electron-hole pairs. The electric field in the depletion region sweeps these photogenerated carriers across the junction: electrons towards the n-side and holes towards the p-side. This movement of charge carriers constitutes a current. This light-induced current adds to the small reverse saturation current (dark current) that flows even in the absence of light. The additional current generated by light is proportional to the light intensity. So, incident light effectively increases the reverse current flowing through the photodiode. (b) Forward current: Photodiodes are not typically operated in forward bias for light detection. (c) Electroluminescence: This is the principle of light emission (LEDs), not detection. (d) Dark current: This is the reverse current that flows in a photodiode even when no light is incident. Light *increases* the current beyond the dark current. Therefore, in a photodiode, light produces an increase in the reverse current. \[ \boxed{\text{Reverse current}} \]