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Semiconductors excitons

  1. Oct 7, 2004 #1
    With regards to semiconductors - am I correct in thinking the term 'exciton' refers to an electron/hole pair?
    Also what does it mean when I am told that the Bohr radius of a silicon exciton is 5nm - how can such an entity have a set radius?
  2. jcsd
  3. Oct 7, 2004 #2
    Yes, this is correct. See this for instance.
    The radius correspond to the mean distance between the electron and the hole I guess.

    [url=http://focus.aps.org/story/v12/st15]The Travels of An Exciton[/url] about
    Near-field Optical Mapping of Exciton Wave Functions in a GaAs Quantum dot
    K. Matsuda, T. Saiki, S. Nomura, M. Mihara, Y. Aoyagi, S. Nair, and T. Takagahara
    Phys. Rev. Lett. 91, 177401
    Last edited by a moderator: Apr 21, 2017
  4. Oct 7, 2004 #3


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    This should have been posted in Atom, Molecules, and Solids, since it's a condensed matter problem.

    An exciton is indeed an electron-hole pair. The reason why there is a "Bohr radius" for it is because this is simply a hydrogenic "atom", i.e. you have an negative charge (the electron) being bound by a central positive charge (the hole). So the Rydberg-type model applies to such exciton as far as the energy-orbital states are concerned.

  5. Nov 6, 2004 #4

    Excitons are indeed an electron-hole pair, and the important feature here is that they are correlated. I.e., there is a significant Coulomb interaction energy, and they are bound such that to separate them, one must supply an energy equivalent to the "exciton binding energy".
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