Hey, Do you want to know what is fermi energy level in semiconductors? If yes. Then keep reading.

Fermi Energy Level.

Fermi energy is the maximum kinetic energy of an electron at 0 K these electrons are called Fermi electrons and energy level is known as Fermi energy level.

• It is always found between the conduction band and valance band
  
  
• Fermi Level is the energy that corresponds to the center of gravity of the conduction electrons and holes weighted according to their energies.
  
  
• In pure germanium semiconductor, the Fermi level is about halfway in the forbidden gap.
  
  
• In an n-type semiconductor, the Fermi level lies in the forbidden gap, very close to the conduction band.
  
  
• In p-type semiconductor, the Fermi level lies in the forbidden gap, very close to the valence band.
  
  
• With rising in temperature the Fermi level moves towards the center of the forbidden gap, for both types of semiconductors.
  
  
• An n-type semiconductor is better than a p-type semiconductor as electrons have more mobility than holes.

Mass Action Law

Under thermal equilibrium, the product of concentration $\mathrm{n}_{\mathrm{e}}$ of free electrons and the concentration $\mathbf{n}_{\mathrm{h}}$ of holes is constant & independent of the amount of doping by donor & acceptor impurity.

$\mathrm{n}_{e} \mathrm{n}_{\mathrm{h}}=\mathbf{n}_{\mathrm{i}}^{2}$

where

$\mathrm{n}_{\mathrm{i}}=$ intrinsic concentration

However, the intrinsic concentration is a function of temperature.

• In n-type semiconductors, the number density of electrons is nearly equal to the number density of donor atoms $\mathrm{N}_{\mathrm{d}}$ and is very large as compared to the number density of holes.
  
  $\mathrm{n}_{\mathrm{e}} \approx \mathrm{N}_{\mathrm{D}}$
  
  $N_{D}>>n_{h}$
  
  
• In p-type semiconductor, the number density of holes is nearly equal to the number density of acceptor atoms $\mathrm{N}_{\mathrm{a}}$ and is very large as compared to number density of electrons.
  
  $\mathbf{n}_{\mathrm{h}} \approx \mathrm{N}_{\mathrm{A}}$
  
  $\mathrm{N}_{\mathrm{A}}>>\mathrm{n}_{\mathrm{e}}$

 
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