Is it possible to shift the fermi level?

Main Question or Discussion Point

I know we can shift the fermi level by doping the material with other elements. In case of semiconductors doping with the pentavalent or trivalent will change the fermi level. But my question is ''can we shift the fermi level, without altering the position of valence band and conduction band?" Thank you.

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ZapperZ
Staff Emeritus
I know we can shift the fermi level by doping the material with other elements. In case of semiconductors doping with the pentavalent or trivalent will change the fermi level. But my question is ''can we shift the fermi level, without altering the position of valence band and conduction band?" Thank you.
This is rather vague. The location of the valence and conduction band are often indicated with respect to the Fermi energy, i.e. in many instances, the Fermi energy is referenced to be "zero". Even if it isn't, when you talk about position of the valence and conduction band, what would be your reference point? Are you talking about simply shifting them simultaneously up and down, keeping their positions relative to each other constant (i.e. keeping the gap the same)? Isn't this similar to just shifting the Fermi level under the rigid band assumption?

Zz.

thank you for your explanation, I think my question is incomplete. I ll get back soon with clear question.

You can shift the chemical potential which is the same as the Fermi energy at T=0 but differs at T>0.

There are methods which I read to change the fermi level, one is doping another is applying pressure but I can't understand how these things change the fermi level. Please explain. Thank you

ZapperZ
Staff Emeritus
There are methods which I read to change the fermi level, one is doping another is applying pressure but I can't understand how these things change the fermi level. Please explain. Thank you
1. Figure out the EXACT definition of "Fermi level".

2. Take a bunch of electrons, and force it into a metal.

3. What just happened to the those electrons? Where did they go as far as the energy level that they occupy in the metal is concerned?

4. What just happened to the Fermi level?

5. How is this different if the metal is replaced by a semiconductor? Will it change the band gap, within the rigid-band assumption?

Zz.