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I Location of donor atom electrons in N-type Silicon

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  1. Oct 22, 2016 #1
    I'm taking a module in solid state electronics and I'm a bit confused with the energy band diagrams. I was told that the region between the top of VB and and the bottom of the CB is the "forbidden gap". However after learning about N-type semiconductors(silicon), I see that the extra electron from the donor atoms have their own energy level right below the bottom of the conduction band in the so called "forbidden gap". How can this be? I'm quite new to solid state and all of its terminology so any help is appreciated.

    Heres a pic: [cant post pic]. its the first one on this page
    http://hyperphysics.phy-astr.gsu.edu/hbase/solids/dsem.html#c2

    dban2.gif
     
  2. jcsd
  3. Oct 22, 2016 #2

    mfb

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    The states are produced by the doping atoms. Undoped semiconductors don't have states in the bandgap, but doped semiconductors do.
     
  4. Oct 22, 2016 #3
    Shouldn't they be in the VB though? Since nothing is meant to be in the Forbidden Gap
     
  5. Oct 23, 2016 #4

    mfb

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    This statement applies to electrons in undoped semiconductors only. It does not apply to modifications of the crystal.

    "I cannot put an apple in a box because there is no box."
    "Here I give you a box"
    "Now I can put an apple in a box."
     
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