confusion in semiconductor diode theory

Discussion in 'General Electronics Chat' started by munna007, Jun 8, 2010.

  1. munna007

    Thread Starter Active Member

    Jul 23, 2008
    hello friends [​IMG]....

    in this picture diode is forward biased. positive terminal of battery repel holes n negative repel electrons , finally electrons n holes recombine n eliminate each other.

    but its said that current flow is due to electrons . but electrons -holes both are eliminated. then how can we say that current flow is due to electrons.
    how can they come out of both terminals of battery as they are eliminated inside ....????

    please clarify my confusion....
  2. Bychon


    Mar 12, 2010
    The hole model is a method to help you understand. If it doesn't help, don't use it.

    Holes don't actually travel. The electrons flow.
  3. elisettynarendra


    May 17, 2010
    hii munna
    what actually happens electrons flow in conduction band i.e., they are free electrons...
    the absence of electron creates a hole ..and the electrons that participates in bonds they just travel through these holes when an electron moves frm left to right holes moves in opp direction...electron moves every where not holes
  4. munna007

    Thread Starter Active Member

    Jul 23, 2008
    thanks for the reply sir.i understan.....what i understand is hole is actually a vacancy of electron ,it cant not move ,but it looks like moving....

    but what about recombibnation.....does it eliminate electron n hole ????
  5. elisettynarendra


    May 17, 2010
    yes recombination deprives us of electrons and ofcourse holes ..the energy released becomes heat in normal diodes case of led it appears as light.
  6. marshallf3

    Well-Known Member

    Jul 26, 2010
    Simple physics of atomic particles.

    Elements which are conductive aren't too picky about swapping one of their electrons for another.

    Push an extra electron into the atom and it ends up in an unbalanced state of slightly negative charge.

    The source atom the extra electron came from now has a "hole" that it's aching to fill so it too can return to equilibrium.

    Since the electron that started all of this was pushed by something like a battery it will meet opposition trying to return via that route, so another (or perhaps even the same) electron passes on to the next atom in line and so on until it fills the hole that was left at the source when this all started.

    Or something to that accord, I'm not the best at explaining some things without being able to draw pictures and knowing where my audience is in their knowledge level.
  7. Wendy


    Mar 24, 2008
    It has to do with doping. There are minor impurities in the semiconductor (hence P and N junctions). When the material is electrically neutral (no electricity) then you have natural excess electrons and holes.

    When it is forward biased the holes are filled, but this is not a permanent state. It lasts as long as the current is flowing, when it stops they revert. So a hole being filed with an electron is a temporary state, nothing is eliminated.