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Effect of Doping on Fermi Energy

  1. Feb 18, 2010 #1
    Effect of Doping on Fermi Energy....

    I was wondering if anyone could give me a clear answer on why doping a semi conductor raises or lowers the fermi energy depending on n or p type semi conductors. There seem to be a few standard ways of explaining this, some to do with charge conservation or the requirement that the probability of occupation be half, but I havn't found one that seems clear to me, any help on this would be much appreciated.
     
  2. jcsd
  3. Feb 18, 2010 #2
    Re: Effect of Doping on Fermi Energy....

    I also faced the same problem but later on found a satisfying answer.
    The answer follows like this.
    The electrons in solid follows fermi-diarac distribution function, which is a function of probability of occupancy Vs Energy of Electron. The function depends upon the absolute temperature and a constant called the fermi-level. So, given that the temperature remains constant, The only way we could account for the increased probability of finding the electron in the valence band in N-type semiconductor is to assume that the constant has now shifted, i.e. the fermi level has now increased i.e. moved towards the valence band. This is the reason for shifting of fermi level due to doping.

    Tell me if you still need more explanation.
     
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