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Semiconductors - role of displaced Silicon or Germanium

  1. Nov 29, 2011 #1
    Semiconductors -- role of displaced Silicon or Germanium

    Revered Members,
    When we dope a pure Germanium or Silicon with pentavalent impurity or trivalent impurity, the dopant replaces Silicon or Germanium and bonds with neighbouring Si or Ge atom. That is Dopant takes the centre position and bonds with 4 neighbouring atoms.
    Now where do that replaced Si or Ge go in the crystal?
     
  2. jcsd
  3. Nov 30, 2011 #2
    Re: Semiconductors -- role of displaced Silicon or Germanium

    I work with a lot of silicon, but I might not be able to answer this, since I am pretty far removed from the manufacturing process. I would imagine the silicon atom that gets displaced becomes mobile and interacts with any other impurities inside the device (such as oxygen impurities that are usually always present, even for high grade silicon), and creates additional energy states within the bandgap (but not a very large concentration, as to not effect greatly the electrical properties of the crystal itself). I am sure with accelerated annealing you can somehow remove these mobile silicon atoms in the crystal (or neutralize their effects). This is all highly speculative, as like I said, I am not involved in the manufacturing process. I would actually like to know the answer myself, so any experts in the growth of semiconductor crystals should chime in.
     
  4. Nov 30, 2011 #3

    Dr Transport

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    Re: Semiconductors -- role of displaced Silicon or Germanium

    The dopant either replaces an atom or becomes an interstitial (lies between the atoms of the lattice)
     
  5. Dec 2, 2011 #4
    Re: Semiconductors -- role of displaced Silicon or Germanium

    Thanks for the replies. @Dr Transport: Does the displaced atom lie stationary when it becomes interstitial?
     
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