Effect of Doping on Fermi Energy

In summary, the effect of doping on fermi energy in semiconductors is dependent on the type of doping (n or p) and the temperature. Doping can either raise or lower the fermi energy, which is the energy level at which electrons have a 50% chance of occupancy. This is due to the shift in the fermi level, caused by the change in probability of finding electrons in the valence band. This shift is necessary to maintain charge conservation and the fermi-diarac distribution function.
  • #1
Cheetox
23
0
Effect of Doping on Fermi Energy...

I was wondering if anyone could give me a clear answer on why doping a semi conductor raises or lowers the fermi energy depending on n or p type semi conductors. There seem to be a few standard ways of explaining this, some to do with charge conservation or the requirement that the probability of occupation be half, but I havn't found one that seems clear to me, any help on this would be much appreciated.
 
Physics news on Phys.org
  • #2


I also faced the same problem but later on found a satisfying answer.
The answer follows like this.
The electrons in solid follows fermi-diarac distribution function, which is a function of probability of occupancy Vs Energy of Electron. The function depends upon the absolute temperature and a constant called the fermi-level. So, given that the temperature remains constant, The only way we could account for the increased probability of finding the electron in the valence band in N-type semiconductor is to assume that the constant has now shifted, i.e. the fermi level has now increased i.e. moved towards the valence band. This is the reason for shifting of fermi level due to doping.

Tell me if you still need more explanation.
 

FAQ: Effect of Doping on Fermi Energy

How does doping affect the Fermi energy in a material?

Doping can either increase or decrease the Fermi energy in a material, depending on the type of doping. N-type doping, which introduces electrons into the material, increases the Fermi energy, while P-type doping, which introduces holes, decreases the Fermi energy.

What is the relationship between doping concentration and Fermi energy?

There is a direct relationship between doping concentration and Fermi energy. As the doping concentration increases, the Fermi energy also increases. This is because more dopants are introduced into the material, leading to a higher number of electron or hole carriers.

Can doping change the type of semiconductor material?

Yes, doping can change the type of semiconductor material. This is because doping introduces impurities that can alter the number of electrons or holes in the material, thereby changing its conductivity and type. For example, adding Boron to Silicon changes it from an N-type to a P-type semiconductor.

How does temperature affect the Fermi energy in a doped material?

As temperature increases, the Fermi energy in a doped material also increases. This is because at higher temperatures, more electrons are excited to the conduction band, leading to an increase in the number of charge carriers and hence, an increase in Fermi energy.

What is the significance of Fermi energy in doped materials?

Fermi energy plays a crucial role in determining the electrical and optical properties of doped materials. It affects the conductivity, carrier concentration, and bandgap of the material. Additionally, Fermi energy also determines the behavior of charge carriers and their interactions with each other and the lattice structure of the material.

Back
Top