Question

Briefly explain how a photodiode detector work.(By diagram)

Answer 1

Working principle of photodiode:

When photons of energy greater than 1.1 eV hit the diode, electron-hole pairs are created. The intensity of photon absorption depends on the energy of photons – the lower the energy of photons, the deeper the absorption is. This process is known as the inner photoelectric effect.

If a photon of sufficient energy enters a depleted region of a diode, it could hit an atom with enough energy to release said electron from the atomic structure, thus creating a free electron and a hole ie an atom with an electron space. The electron has a negative charge, and the hole a positive charge. These electron-hole pairs drift apart and are swept from the junction - due to the built-in electric field of the depletion region. As a result, the holes move toward the anode and the electrons move toward the cathode, thereby producing photocurrent.

The sum of photocurrents and dark currents, which flow with or without light, is the total current passing through the photodiode. The sensitivity of the device can be increased by minimizing the dark current.