Semiconductors excitons

1. Oct 7, 2004

timmyeatchips

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. Oct 7, 2004

humanino

Yes, this is correct. See this for instance.
The radius correspond to the mean distance between the electron and the hole I guess.

example of research thema
The Travels of An Exciton 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

3. Oct 7, 2004

ZapperZ

Staff Emeritus
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.

4. Nov 6, 2004

toozie

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".