Hi,
I am new to the forum. And this is my first post.
Moss-Burstein shift:- The effect happens in semiconductors. If you nominally dope the semiconductor (say n-type), the Fermi level lies below the conduction band edge and above the occupied donor states. If you increase the doping more and more, and when you reach a degenerate level of doping, Fermi level moves into the conduction band. The effect becomes more when you increase the donor concentration more. Now, if you try to measure the band gap by absorption measurement, an electron at the top of the valence band can only be excited to a state above the Fermi level (which now lies in the conduction band) because all the states below the Fermi level are occupied donor states. You cannot excite electrons into the occupied states as Pauli's exclusion principle forbids it. Thus what you will observe is increased band gap. ie.,
Observed band gap = Actual band gap + MB shift.
Hope this explains you.
-Jithesh
