Briefly explain its working. Draw its V - I characteristics for two different intensities of illumination ?
Current AB that flows when no light is incident is called dark current.
When photons of light having energy hν fall on the photodiode, more electrons from the valence band move to the conduction band, provided hv is greater than the forbidden energy gap.
The current in the circuit increases. As the intensity of light is increased, the current goes on increasing (represented by the part BC).
- When the current does not increase with the increase in intensity of light, the photodiode is said to be saturated. The portion CD of the graph represents the saturated current.