Band Diagram of a Metal-Semiconductor Contact

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SUMMARY

The discussion centers on the band diagram of an ideal Metal-Semiconductor contact, specifically when the work function of the metal (\Phi_{M}) is less than that of the semiconductor (\Phi_{S}) in a p-type semiconductor. It is established that the Fermi level intersects the intrinsic level at the metallurgical junction due to charge transfer, which aligns the Fermi levels of both materials. Electrons migrate from the metal to the p-type semiconductor, causing downward bending of the intrinsic level, conduction band, and valence band. This scenario represents a specific case where charge transfer is sufficient to invert the p-type semiconductor to an intrinsic state at the surface, while the band bending diminishes deeper in the material.

PREREQUISITES
  • Understanding of semiconductor physics, particularly p-type semiconductors.
  • Knowledge of work functions in metal-semiconductor systems.
  • Familiarity with band theory and energy band diagrams.
  • Concept of Fermi level alignment in materials.
NEXT STEPS
  • Study the principles of charge transfer in metal-semiconductor junctions.
  • Explore the effects of work function differences on band bending.
  • Learn about the behavior of intrinsic and p-type semiconductors at junctions.
  • Investigate the implications of band diagrams in electronic device design.
USEFUL FOR

This discussion is beneficial for materials scientists, semiconductor physicists, and electrical engineers involved in the design and analysis of metal-semiconductor interfaces in electronic devices.

maverick280857
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Hi

In the band diagram of an ideal Metal Semiconductor contact with \Phi_{M} &lt; \Phi_{S} (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.
 
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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.
 

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