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Photodiode definition
Photodiode definition – a type of semiconductor diode that serves as a photo detector. The purpose of a photodiode is to convert power from photons of light into electric current. The generation of electric current is created when the power of photons of light is absorbed by the surface of a semiconductor. A negligible electric current is also generated without the participation of light sources. Increasing the absorption area of the photodiode increases the absorption of light but also increases the response time, i.e. the time to produce the intensity. Its electrical properties are dependent on the light radiation that is illuminating it. It is easy to recognize this component among other semiconductor diodes due to its characteristic housing with transparent window. Internal photodiode component construction is based on the p-n junction or p-i-n structure (p-i-n-with an intrinsic or undoped layer between two p-n doped semiconductor crystals). The photodiode is used widely due to its simplicity of operation and relatively low production cost.
Photodiode working principle
Energy is delivered to the photodiode junction while it is being illuminated by photons (light) – injection of minority carriers takes place, wherein the pairs of hole and electron are generated. It causes the generation of current, which is proportional to the light flux that “is put” on the photodiode (photoelectric effect). Total current that flows through the junction is the sum of two components: the saturation current (dark current) and current dependent from illumination intensity. The free electrons are attracted by the positive charged particles on the n-type area border, while the holes penetrate into the p-type area.
