Photo Detectors

p-n Photodiodes A reverse biased p-n junction consists of a region known as depletion region that is devoid of free charge carriers. When light impinges on one side of such a p-n junction, electrons absorb light and make a transition from valence band to conduction band. Thus, electron-hole pair is created through light absorption. The electrons and holes generated inside the depletion region accelerate in opposite directions due to the reverse bias. This gives rise to a current flow in an external circuit and this current flow is known as the photocurrent.

p-n photodiodes

p-n photodiodes

p-n photodiodes

p-n photodiodes

p-i-n photodiodes

p-i-n photodiodes

Avalanche Photodiodes (APD)

Avalanche Photodiodes (APD)

Receiver Noise

Shot Noise

Thermal Noise

Thermal Noise

Noise in p-i-n Receivers

Noise in APD Receivers

Avalanche Photodiodes (APD)