Semiconductors

Discussion in 'Homework Help' started by aelec, May 20, 2012.

  1. aelec

    Thread Starter New Member

    May 20, 2012
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    The formulae for the photocurrent in an illuminated photodetector is I=qAgop(Ln+Lp+W). Why is it W (depletion width) and not 2*W since both holes and electrons are optically genereted in the depletion region? Thanks :D
     
  2. crutschow

    Expert

    Mar 14, 2008
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    I think it's because the hole is created when the electron vacates a location in the semicondtor which creates the lack of an electron at that position (a hole). So each absorption of a photon creates one hole-electron pair.
     
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  3. aelec

    Thread Starter New Member

    May 20, 2012
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    Thank you for your answer, but let me make my question a little bit clearer. We have 1 electron and hole created, right? Now, both holes and electrons will move due to the electric field, so it a double contribution to the current. Why don't we consider 2*W?
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    1 hole and 1 electron, not X2. When that one electron moves into the hole, it is filled.
     
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