Photodiode

A photodiode is a semiconductor device that converts incident light into electrical current or voltage. Its output arises when absorbed photons create charge carriers that are separated by an internal or applied electric field.

Photovoltaic effect: The generation of voltage or current in a material when it absorbs light. Photodiodes produce electrical output through this conversion of absorbed light into charge separation.
Semiconductor: A material whose electrical conductivity lies between that of a conductor and an insulator and can be controlled by doping or fields. Photodiodes rely on semiconductor properties to generate and transport light-driven charge.
Avalanche photodiode: A photodiode operated at high reverse bias so impact ionization internally multiplies photogenerated carriers. It adds internal gain, unlike ordinary photodiodes, at the cost of excess noise and bias complexity.
Photodetector: A device that detects light and converts its presence or properties into a measurable output. Photodiodes are a widely used semiconductor class of photodetector.
Photoconductivity: An increase in a material’s electrical conductivity caused by absorbed electromagnetic radiation. Photogenerated carriers raise conductivity and contribute to a photodiode’s measurable current.
Doping (semiconductor): The deliberate addition of impurities to a semiconductor to control its carrier concentration and electrical behavior. Dopant profiles create the junction fields and carrier regions used in photodiodes.
PIN diode: A diode with intrinsic semiconductor between p-type and n-type regions, often used for fast light detection. Its wide intrinsic layer improves carrier collection and is a common photodiode architecture.
Fiber-optic communication: The transmission of information as light through optical fibers. Photodiodes convert received fiber-optic signals back into electrical signals.
P–N junction: A semiconductor interface between regions with different dopant types, forming a depletion region and an internal electric field. Its depletion-region field separates photogenerated electrons and holes.
Depletion region: A semiconductor junction region depleted of mobile carriers, containing fixed ionized dopants and an electric field. Photons absorbed here generate carriers that the field can rapidly separate.

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