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Doping of semiconductors

  1. Dec 21, 2011 #1
    Are there any other atomic elements that are capable for doping apart from the trivalent and pentavalent atoms? If any why is it not preferred over boron and arsenic?
     
  2. jcsd
  3. Dec 23, 2011 #2
    Hey!!No replies at all.. Say something even if you feel like the question is silly.... I really mean it to ask the question...
     
  4. Dec 25, 2011 #3
    I've never heard of anything outside these two groups, but it does seem that I remember phosphorus being used. Also, you might look into the doping of LEDs. They get some pretty odd mixes
     
  5. Dec 25, 2011 #4

    dlgoff

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    Last edited: Dec 25, 2011
  6. Dec 26, 2011 #5

    es1

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    I just ran across this in a foot note in a textbook I was reading the other day. They claim difficulties in handling the elements during fabrication prevent others from being used widely.

    The meat of the note specifically says, "These difficulties include limited solid solubility and incomplete dopant ionization. For example Indium-doped silicon suffers from the latter problem. ... Random thermal vibrations suffice to ionize boron, phosphorus, arsenic, and antimony in silicon."

    This is from "The Art of Analog Layout" 2nd Edition by Alan Hastings pg 8. You might be able to find the excerpt in Google books.

    They recommend reading H. Tian "A comparative study of Indium and Boron Implanted Silicon Bipolar Transistors," IEEE Trans. on Electric Devices Vol. 48 #11 pp 2520-2524. for more information.
     
  7. Dec 28, 2011 #6
    Thanks..to all, that was something!! I welcome more ideas if any.. But to this point am okay..
     
  8. Dec 31, 2011 #7
    In fact, any material will dope the semiconductor if they have energy level(s) which lies within the bandgap. But the issue is with the degree of doping. Apart from the well known dopants like (Boron and Phosphorus) the dopant energy level is much below the CB of above the VB. Thus complete ionization does not occur, requiring much greater dose of dopants.

    There are also other issues. A group II or group VI impurity differs much in atomic radius than group IV Si/Ge, creating compressive or expansive stresses. This will generate defects and/or alter the carrier mobility degrading the quality of the semiconductor.

    Even for legitimate dopants, fab labs have to deal with many issues. Like the activation energy is very high for In. Al is easily oxidized. Diffusion of Ga in SiO2 is high requiring thicker oxide mask. P is 10 times diffusible in Si than Sb and As making the doping profile difficult to control. Even As is sometimes discarded for being poisonous.

    Thus, when it comes to select a dopant, its selecting one which ionizes well, produces little defects, can be controlled well, has less poison hazard.
     
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