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Metal-Semiconductor Junction

  1. Feb 4, 2010 #1
    Hi,

    I have a questions regarding semiconductor-metal junctions that has been left unresolved. I hope that you can offer me an explaination.

    I know that when a metal and n-doped semiconductor are in contact upward band bending occurs. This is because the Fermi levels in the two materials must be the same. This causes a diffusion force on the electrons. Eventually positive charge builds up near the junction which halts the diffusion current, thus establishing equilibrium.

    My question is: what causes the shape of the potential? Why is it easier for electrons to flow in one direction than the other? The potential seems to undergo a steep drop on the metal side and a gradual drop on the semiconductor side. What causes this?

    Thanks,
    abomination5
     
  2. jcsd
  3. Feb 5, 2010 #2

    DrDu

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    Science Advisor

    I would say because the screening length in the metal is much shorter than in the semiconductor due to the higher electron density.
     
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