IGNOU BPHET 143 2026 - Describe the construction of a photodiode with appropriate diagram. Wh

Question

Describe the construction of a photodiode with appropriate diagram. What is the minimum frequency (in Hertz) of the photons detectable by a photodiode made of a semiconductor with 2.5 eV bandgap?

19 Jan 2026

Answer :

Word Count : 286

A photodiode is a semiconductor optoelectronic device that converts incident light into an electrical signal. It is typically fabricated using a p–n junction or a p–i–n structure made from materials such as silicon, germanium, or gallium arsenide. In construction, a thin p-type layer is formed on an n-type substrate (or vice versa), creating a depletion region at the junction. This depletion region is the active area where light absorption takes place. The device is usually operated under reverse bias to widen the depletion layer, reduce junction capacitance, and improve response speed. A transparent window or lens is provided on the top surface to allow photons to

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