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Explain how a depletion region is formed in a junction diode. |
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Answer» Formation of depletion layer: At the junction there is diffusion of charge carriers due to thermal agitation; so that some of electrons of n-region diffuse to p-region while some of holes of p-region diffuse into n-region. Some charge carriers combine with opposite charges to neutralise each other. Thus near the junction there is an excess of positively charged ions in n-region and an excess of negativelycharged ions in p-region. This sets up a potential difference called potential barrier and hence an internal electric field Ei across the junctions. The field Ei is directed from n-region to p-region. This field stops the further diffusion of charge carriers. Thus the layers (≈10-4cm to 10-6cm) on either side of the junction becomes free from mobile charge carriers and hence is called the depletion layer. |
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