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how can holes move from p-region to n-region during the formation of p-n junction?i feel that they cannot move since they are only electron vacancies.is there any equivalent movement of electrons?pls send me a detailed concept of the formation of pn junction.

how can holes move from p-region to n-region during the formation of p-n junction?i feel that they cannot move since they are only electron vacancies.is there any equivalent movement of electrons?pls send me a detailed concept of the formation of pn junction.

Grade:12

1 Answers

Ravi
askIITians Faculty 69 Points
9 years ago
P-njunctions are formed by joiningn-type andp-type semiconductor materials. Since then-type region has a high electron concentration and thep-type a high hole concentration, electrons diffuse from then-type side to thep-type side.
Similarly, holes flow by diffusion from thep-type side to then-type side. If the electrons and holes were not charged, this diffusion process would continue until the concentration of electrons and holes on the two sides were the same, as happens if two gasses come into contact with each other. However, in ap-njunction, when the electrons and holes move to the other side of the junction, they leave behind exposed charges ondopantatom sites, which are fixed in the crystal lattice and are unable to move. On then-type side, positive ion cores are exposed. On thep-type side, negative ion cores are exposed. An electric fieldÊforms between the positive ion cores in then-type material and negative ion cores in thep-type material. This region is called the "depletion region" since the electric field quickly sweeps free carriers out, hence the region is depleted of free carriers. A "built in" potential Vbidue toÊis formed at the junction.

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