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A photodiode is a device that helps in conversion of light into electric current. Made of semi-conductor material and containing a p-n junction, it is designed to function in reverse bias. Current is produced in the photodiode when photons are absorbed and a small amount of current is also produced when there is no light present. With increase of the surface area, photodiodes have slower response times. Photodiode technology has been successfully and widely used due to its simple and low-cost rugged structure.
Techopedia Explains Photodiode
The important features of photodiodes are:
- Speed/bandwidth
- Dark current
- Maximum allowed photocurrent
- Responsivity
- Active area
There are different types of photodiodes such as:
- PN photodiode – The first type of photodiode to be developed, but not as widely used as others due to better performance parameters of other types of photodiodes
- Avalanche photodiode – Provides very high gain levels but comes with high noise levels
- PIN photodiode – One of the most widely used photodiodes, it offers lower capacitance and efficiently collects light photons better than PN photodiodes
- Schottly photodiode – Based on the Schottky diode, it offers small diode capacitance as well as has very high speed capability
Photodiodes have two different operation modes, namely photovoltaic mode and photoconductive mode. In photovoltaic mode, dependence on light is non-linear and the dynamic range achieved is fairly small. Maximum speed is also not obtained in photovoltaic mode. In photoconductive mode, the dependence on the light is very linear. Reverse voltage has no significant influence on light, but has a weak influence on dark current (current achieved without light).
Photodiodes are widely used in the electronics industry, especially in detectors and wide bandwidth optical telecommunications systems.
