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PN junction charge difference

  1. Sep 8, 2013 #1
    In a PN junction, if the P doped side becomes negatively charged with respect to the N doped side, does this mean that the application of an external metal wire, from the P side to the N side would cause current flow in that wire?

    Gien that the depletion region can be readily made at least 0.1 mm in size, and integrated circuitry can be made much, much smaller. Could a wire be periodically switched to connect the regions, allowing for regeneration of charge when the wire is open?
  2. jcsd
  3. Sep 8, 2013 #2


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    Gold Member

    Hi M-smurf
    I suppose what you are considering is that the depletion zone similar to a battery or charged capacitor and that it should be possible to short circuit the depletion zone or attempt to grab some energy from it externally.

    The holes from the P-side combine with the electrons from the n side leaving an area that has no charge carriers. Subsequentially, outside the depletion zone, the p side has an area of negatively charges ions, and the n side has an area of positively charge ions. At some point the electrostatic field set up by these ions becomes great emough to prevent any more electron or hole movement.

    If you connect a wire directly between the 2 sides, the electrostatic field will still prevent hole and electron migration even though there is now a "short circuit path available. Whether an electron from the n side tries to take the path to the p side either throough the depletion zone or through the wire, it will still be subject to the negative part of the field from the negative ions on the p side. And vice versa for a hole from p to n side.

    hope that helps.
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