The Fermi energy is the energy of highest occupied state at zero temperature by 
therefore, it is in semiconductors always the top of the valence band.

Everything else will be an arbitrary choice !  (Or are there any occupied 
states inside of the gap ? ;-)

Do not confuse the Fermi energy with the chemical potential that enters the 
Fermi-Dirac distribution.

I guess the thing you call "Fermi-level" is never clearly in the middle of the 
band gap (or only by chance), 
because its position depends not only on the temperature and the doping of the 
semi conductor but also
on the shape of the density of states in the valence and conduction bands.

Too bad that sometimes even textbooks use "laboratory slang" rather then clear 
well defined expressions.


DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
Max Planck Institute for Chemical Physics of Solids
01187 Dresden
Von: Wien [] im Auftrag von []
Gesendet: Donnerstag, 20. Oktober 2016 10:33
Betreff: [Wien] Fermi level

Dear Wien users,
I have searched in the archives to understand why the fermi level is at the 
maximum of the valence band in band structure plot of a semiconductor, I found 
that it was an arbitrary choice but untill now i can't explain this from a 
physical point of view since for me the fermi level must be in the middle of 
the gap.

Thank you for your help
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