Class 12th Physics 2017 Set1 Delhi Board Paper Solution
Write the two processes that take place in the formation of a p-n junction. Explain with the help of a diagram, the formation of depletion region and barrier potential in a p-n junction.
During the formation to p-n Junciton two processes take place:
(i) Diffusion: There is difference in concentration of charge carriers in p-n region. The e- from n and holes from p region diffuse. Motion gives rise to diffusion current.
(ii) Drift: Diffusion of e- from n region results in ionised donor atoms (+ve). It is immobile as it is bound to surrounding atoms. Positive space charge region near junction in n region is formed.
Electrons are majority carriers in n type semiconductors and holes are majority carriers in p-type semiconductors. Loss of electrons in n region and its gain. Polarity fo potential opposes further flow of carrier i.e., it tries to attain equilibrium. As this potential is of preventive nature, so called barrier potential.
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