A) depletion of positive charges near the junction
B) concentration of positive charges near the junction
C) depletion of negative charges near the junction
D) concentration of positive and negative charges near the junction
Correct Answer: D
Solution :
In a \[p-n\] junction diode, majority carriers are holes on \[p\]-side and electrons on \[n\]-side. Holes, thus diffuse to \[n\]-side and electrons to \[p\]-side. This diffusion causes an excess positive charge in the \[n\]-region and an excess negative charge in the \[p\]-region near the junction. This double layer of charge creates an electric field which exerts a force on the electrons and holes, against their diffusion. This electric field becomes strong enough as diffusion proceeds to stop it. In the equilibrium position, there is a barrier, for charge motion with the \[n\]-side at a higher potential than the \[p\]-side. The junction region has a very low density of either \[p\] or \[n\]-type carriers, because of inter diffusion. It is called depletion region. There is a barrier \[{{V}_{B}}\] associated with it. This is the potential barrier.
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