Fermi level in n-type or p-type semiconductors

In summary, the conversation discusses the concept of Fermi level in semiconductors and its proximity to the conduction and valence bands in n-type and p-type semiconductors. It is clarified that the Fermi level does not necessarily have to be a possible energy level for electrons and its positioning is determined by the presence of additional electrons or holes. It is also explained that applying a potential on the semiconductor materials can cause a shift in the Fermi level due to changes in electron energies.
  • #1
Cathyzhang
2
0
Hi, everyone. I'm learning basic theories about semiconductors but can't quite understand the concept of Fermi level. is this just a imaginary energy level or true existence? and why Fermi level is close to the conduction band of n-type semiconductor and valence band of p-type semiconductor? the last question is, if applying a potential on the semiconductor materials, the Fermi level will shift up and down with the increase or decrease of the voltage-why?
thanks _Cathy:smile:
 
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  • #2
is this just a imaginary energy level or true existence?
It does not have to be a possible energy level for electrons.
"imaginary" versus "true" is not physics.

and why Fermi level is close to the conduction band of n-type semiconductor and valence band of p-type semiconductor?
I think this is easier to see if you imagine an additional energy level in the bandgap. Where would it have to be to be 50% filled?
For n-type semiconductors, close to the conduction band, as you have additional electrons there.
For p-type semiconductors, close to the valence band, as you have additional holes there.

the last question is, if applying a potential on the semiconductor materials, the Fermi level will shift up and down with the increase or decrease of the voltage-why?
A voltage changes electron energies.
 
  • #3
mfb said:
It does not have to be a possible energy level for electrons.
"imaginary" versus "true" is not physics.

I think this is easier to see if you imagine an additional energy level in the bandgap. Where would it have to be to be 50% filled?
For n-type semiconductors, close to the conduction band, as you have additional electrons there.
For p-type semiconductors, close to the valence band, as you have additional holes there.

A voltage changes electron energies.

Thanks! that's help :)
 

What is the Fermi level in a semiconductor?

The Fermi level is a measure of the energy in a semiconductor that is occupied by electrons at a given temperature. It is also referred to as the chemical potential of the electrons.

What is the difference between n-type and p-type semiconductors?

N-type semiconductors have an excess of electrons, while p-type semiconductors have a deficiency of electrons, known as holes. This difference is created by doping the semiconductor with impurities, such as phosphorus for n-type and boron for p-type.

How does the Fermi level change in n-type and p-type semiconductors?

In n-type semiconductors, the Fermi level is closer to the conduction band due to the excess of electrons. In p-type semiconductors, the Fermi level is closer to the valence band due to the deficiency of electrons.

What is the significance of the Fermi level in semiconductors?

The Fermi level plays a crucial role in determining the conductivity and other properties of semiconductors. It also helps in understanding the behavior of electrons in the material and the formation of energy bands.

How does temperature affect the Fermi level in semiconductors?

As temperature increases, the Fermi level moves closer to the middle of the energy band gap in semiconductors. This is due to the increased thermal energy of the electrons, which allows them to occupy higher energy levels in the band structure.

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