Band Diagram of a Metal-Semiconductor Contact

[maverick280857]

Hi

In the band diagram of an ideal Metal Semiconductor contact with [itex]\Phi_{M} < \Phi_{S}[/itex] (work function of metal < work function of semiconductor) and a p-type semiconductor, why does the Fermi Level intersect the Intrinsic level right at the metallurgical junction?

Thanks.

 

[sokrates]

There's no requirement as such. The only requirement is that after the necessary charge transfers, the Fermi levels of both materials have to align.

In this particular case, electrons would move from the metal to the p-type SC, because of the particular work functions you chose, and the intrinsic level (as well as the conduction band and the valence bend) would bend downwards. But there's no requirement for the fermi level to cross the intrinsic level right at the junction. This situation would correspond to an extremely specific case, where the charge transfer is 'just enough' to invert the p-type semiconductor to an 'intrinsic' semiconductor at the surface!

of course, when you move along the bulk ( deep down), the band bending would vanish and you'd go back to your original p-type distribution.

 

[charng]

Hi there,

The Fermi level represents the energy level at which electrons in a material have a 50% chance of being occupied. In an ideal metal-semiconductor contact, the work function of the metal is lower than the work function of the semiconductor, meaning that the metal has a higher concentration of free electrons compared to the semiconductor. This results in a flow of electrons from the metal to the semiconductor, creating a depletion region at the interface.

At the metallurgical junction, the Fermi level of the metal and the Fermi level of the semiconductor align due to the diffusion of electrons. This equilibrium condition is known as the Fermi level pinning effect. As a result, the Fermi level of the semiconductor intersects with the intrinsic level, which represents the energy level at which there are an equal number of electrons and holes in the material.

This intersection of the Fermi level and intrinsic level at the metallurgical junction indicates that there is no net flow of electrons or holes across the junction, creating a barrier for further electron transfer. This barrier, known as the built-in potential, is necessary for the formation of a stable metal-semiconductor contact.

I hope this helps to explain the positioning of the Fermi level at the metallurgical junction in a metal-semiconductor contact. Let me know if you have any further questions.