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yasir.ustb
yasir.ustb is offline
#2
Oct31-11, 05:53 AM
P: 12
Quote Quote by *FaerieLight* View Post
Hi,

Can someone please tell me if it is true that in heavily doped pn junctions, the electric field that prevents further diffusion of holes and electrons is set up more quickly than in less heavily doped pn junctions? Is this essentially because the holes and electrons recombine more quickly and very near the join between the p and n type semiconductors, which occurs because the charges don't need to travel very far before they recombine?
So then is this the reason why depletion layers for such pn junctions are narrower than for less heavily doped pn junctions?

Thanks a lot.
Actually, In heavily doped P-N junction there are lot of donor (+ive charge) and accepters (-ive charge) in n and p region respectively. when junction is formed the electron from n side to p side to recombine with holes and vice versa, leaving behind -ive donor in n region and +ive acceptors in p region. Theses +ive and -ive charges setup an internal Electric filed Ein which prevent the further diffusion of charge carriers(electron and holes).. So in the case of heavily doped of p-n junction, only less recombination of electron and holes is required to set up the Electric field which prevent the further diffusion, resulting in narrow depletion region... while is lightly doped large no. recombination of electron and holes is required which result in wide band gap.