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Semiconductor Band Gap

  1. Sep 4, 2008 #1
    In the first diagram on this Hyperphysics page, the band gap in a semiconductor is shown.

    What is the corresponding Fermi momentum? If you plug E_F into the dispersion relation, you get no solution for k_F, right?

    I ask because an equation is given with a sum of all k such that k < k_F, and there is a band gap. Does one sum over all k?
  2. jcsd
  3. Feb 15, 2009 #2
    late response ;-)

    I do not know which equation you mean, but generally if you sum all k in a full band you end up with zero net momentum. This is the same as saying: a full band is not contributing to electrical conduction. In the bandgap, there are no electrons thus there is no contribution to the total momentum. At T=0, there are no elevtrons in the conduction band, so also no net momentum there

    as far as I can see it, you can only use the concept of the Fermi momentum if the Fermi energy is at least few kT inside a band. This is the situation, you mya encounterin metals or degenerated (=very heavily doped) semiconductors

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