What Are Excitons and Their Bohr Radius in Semiconductors?

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Discussion Overview

The discussion revolves around the concept of excitons in semiconductors, specifically addressing their definition as electron-hole pairs and the significance of the Bohr radius associated with them. Participants explore the theoretical implications and models related to excitons, including their binding characteristics and energy states.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants confirm that excitons refer to electron-hole pairs in semiconductors.
  • There is a discussion about the Bohr radius of excitons, with one participant suggesting it represents the mean distance between the electron and the hole.
  • Another participant explains that the Bohr radius concept applies because the exciton can be modeled similarly to a hydrogen atom, where the electron is bound to the hole by Coulombic attraction.
  • One participant emphasizes the correlation between the electron and hole due to significant Coulomb interaction energy, noting that separating them requires energy equivalent to the exciton binding energy.

Areas of Agreement / Disagreement

Participants generally agree on the definition of excitons as electron-hole pairs and the relevance of the Bohr radius concept. However, the discussion remains open regarding the implications and interpretations of these concepts, with no consensus on all aspects presented.

Contextual Notes

The discussion touches on theoretical models and assumptions related to excitons, including the applicability of hydrogenic models and the nature of Coulomb interactions, but does not resolve the complexities involved in these interpretations.

timmyeatchips
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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?
 
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Yes, this is correct. See http://www.wordiq.com/definition/Exciton for instance.
The radius correspond to the mean distance between the electron and the hole I guess.

www.iapp.de/~mi-hoffm/spex/ExModels/exmodels.html[/URL]
[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
 
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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.

Zz.
 
Excitons

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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