which of the following statement, related to a P-N junction, are correct? (A)The

Question

which of the following statement, related to a P-N junction, are correct?

(A)The direction of the bulit in electric field in the depletion layer is from the n-type toward the p-type region.

(B)At reverse bias, the fermi level is constant for the entire pn juction.

(C)A nonzero current of minority carriers flow thru the pn junction at zero bias.

(D) At reverse bias, the depletion-layer width.

(E) The number of electrons able to overcome the energy barrier at the pn junction increases exponentially with the forward-bias voltage

Explanation / Answer

A. True ,Explanation :-When the P and N-regions are brought into contact, the electrons starts to flow from N-regions towards P-region.And holes start to flow from P-region towards the N-region.Because of loss of electrons, the N-region acquires a net positive charge due to the uncovered positively charged donor atoms and P-region acquire a net negative charge due to uncovered negatively charged acceptor atoms.And this continues back&forth until number of electrons which have crossed the junction have large enough electrical charge to prevent any more charge carriers from crossing over the junction. Hence a state of equilibrium i.e. Electric field will occur producing a “potential barrier” zone around the area of the junction as the donor atoms (i.e of N region) repel the holes and the acceptor atoms (P-region) repel the electrons. In this way electric field is generated from n-regions to p-regions

B.False :for any bias voltage whether it is reverse or forward ,the Fermi level of the side which is at higher electric potential will have lower electron energy than the side at lower potential. So the Fermi level is not uniform through out the junction. As in reverse bias the p-side potential is less than N-side potential.

C.True:as Zero Bias means no external voltage potential is applied to the PN junction diode
The electric field that exists (N-region to P-region) doesn't allows the diffusion of any more majority carriers across the junction. But, this Electric field assists minority carriers (few free electrons in the P-region and few holes in the N-region) to drift across the junction.

D .Increases

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