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Semiconductor Electronics: Materials, Devices and Simple Circuits
Question
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Assertion:  A p-n junction with reverse bias can be used as a photo-diode to measure light intensity. 

Reason:  In a reverse bias condition the current is small but it is more sensitive to change in intensity of incident light.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.

Answer

A.

If both assertion and reason are true and reason is the correct explanation of assertion.

The assertion and reason both are true.

A photodiode is a p-n junction. When a photon of sufficient energy strikes the diode, it creates an electron-hole pair.

By using reverse-bias condition, this reduces the response time because the additional reverse bias increases the width of the depletion layer, which decreases the junction's capacitance. The reverse bias also increases the dark current without much change in the photocurrent.

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