Band Gap.md

Band Gap

Band gap is the minimum energy required to excite an electron in the valence band to a state in the conduction band where it can participate in conduction[[Band Gap#^Ref-1|[1]]]. An important parameter in band theory is Fermi Level which is the chemical potential at $T=0$ or can also be understood as the top of the available electron energy levels at that temperature. The position of the Fermi level in relation to the conduction band determines the electrical properties of the substance.

![[Pasted image 20220912143526.png]]

Fermi Level

Fermi Level is the term used to describe the top of the collection of electron energy levels at absolute zero temperature[[Band Gap#^Ref-2|[2]]]. According to the Pauli exclusion principle, electrons being fermions cannot exist in identical energy states. So, at absolute zero they pack into the lowest available energy states and build up a Fermi sea of electron energy states. The Fermi level is the surface of this sea of electron energy states.

References

http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/band.html#c5 ^Ref-1

http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/Fermi.html#c2 ^Ref-2