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PN Junction Question - Current

  1. Oct 22, 2007 #1
    I guess my most general question would be:

    Given a P/N junction. Lets say two circular discs, one P one N. There obviously exists some Vgap, and applying some voltage across it excites the electrons, then it emits light (very basic LED or something).

    Now, what if you took a piece of wire, and coiled it, and put it around the diode. Lets say for arguments sake you theoretically only put the coil around the N part.

    Now you run a current through the coil. This creates a B field in the +-Z direction for the N part, which, since semiconducting, creates a current in the Lz direction (loop about the Z axis). Now this current doesn't really go anywhere, right? It just spins around and around.
    What I'm wondering is : Would this induced loop current have ANY effect on the Vgap energy (the barrier). I'm figuring perhaps theres something due to scattering, or something else.
    I have a feeling it would really only change the free electrons, which might change the intensity, but not the energy of the gap.

    Can someone tell me?
  2. jcsd
  3. Oct 24, 2007 #2


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    Staff: Mentor

    I don't believe it will make any difference since the magnetic field lines are parallel with the normals to the planes of the n-p junction if I'm reading the description correctly. And I take it the current is steady/constant?
  4. Oct 25, 2007 #3
    Indeed. Thats what I was wondering. There would be both the current across the junction, as well as a circular current(which was induced by the field). This is purely a hypothetical. I didn't think it would have any effect, but I couldn't reason out why. I guess the fact that the charge carriers are mobile before a potential is applied across the junction doesn't make them and more or less energetic.

    Same idea would work if you had a very very long p/n junction and ran a cross current tangential to the junction normal. Don't know if there would be any difference. Their current bands should be the same, dispersion relations the same; I'm not sure why I thought it would do anything. I guess there just seemed to be something where, if the P part has a cross current, wouldn't SOMETHING change?
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