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Metal Semiconductor Contact

Robotduck

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Assume n type semiconductor:
1) Can the fermi level of metal change when it makes contact with the Semiconductor ? What assumptions do we make in ideal situation ?
2) Is the Schottky Barrier in Metal Semiconductor contact remains constant with an applied forward or reverse voltage ?
3) On what reasons, do we say that the metal semiconductor junction is forward biased when applying positive on the metal side and negative at the semiconductor side, since both have electrons as a majority carriers .

Thank you in advance !!
 

timof

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1. Normally, the Fermi level of a metal is a basic material property of the bulk, so it should not change in the presence of a contact with semiconductor.

2. No, it changes due to the image charge effect.

See, for example, here (or in any textbook on semiconductor device physics):

https://ecee.colorado.edu/~bart/book/barlow.htm

3. At forward bias, the barrier for electrons going from the semiconductor to the metal decreases, so current increases (nearly exponentially).
At reverse bias, the barrier for electrons going from metals to semiconductor stays (about) constant, so the current does not increase (much).
 
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