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Question about semiconductor

  1. Aug 17, 2008 #1
    I have read this paragraph:
    "When an electrical field is applied to a metal, a potential drop associated with that field must take place outside the metal, usually at the metal contacts: any change in potential inside the metal is prevented by the mobility and number density of the carriers. This can be understood from Poisson equation"
    (Hamnett and Christensen)

    I have some question which need your help:
    1. Why potential drop must "take place outside" the metal ?
    2. Why "mobility and density of carriers" prevent such thing to happen?
    3. Poisson equation is the second derivative of the potential in the x direction = -p (epsilon*const) where p = density of charge carrier and epsilon = dielectric function of the semiconductor. What are the relation between this equation the above paragraph?

    Thank you very much!
  2. jcsd
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