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Increase in doping concentrations resulting in a decrease in mobility?

  1. Feb 22, 2014 #1
    1. The problem statement, all variables and given/known data
    So in one of our practice problems it states that as we increase the doping concentrations, the result will be a decrease in mobility.
    I9OgoC8.png

    However, I thought that when you increase doping concentrations, there will be a higher concentration of carriers available for conduction and thus the conductivity increases. So this should result in an increase in mobility? Also, when they say doping concentrations, it can either be p or n type dopants right?
     
  2. jcsd
  3. Feb 22, 2014 #2

    ehild

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    The conductivity increases, but the mobility decreases. The conductivity is proportional to the concentration of free carriers, about equal to the doping concentration; and also proportional to the mobility. But the mobility decreases with the doping, as the free carriers collide with the impurities more frequently, so the drift velocity decreases.

    ehild
     
  4. Feb 22, 2014 #3
    Oh wow, that's actually pretty cool, thanks!
     
  5. Feb 22, 2014 #4

    ehild

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    You are welcome:smile:

    ehild
     
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