Doping Silicon with Arsenic

Discussion in 'Homework Help' started by philliesws10, May 20, 2013.

  1. philliesws10

    Thread Starter New Member

    Mar 31, 2013
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    0
    Hey all!

    I have the following question:

    A sample of silicon is doped with arsenic such that the concentration of free electrons is 2.3*10^15 cm-3 when the temperature is 311 K. Determine the concentration of holes in the sample at that temperature.

    Now from what I know, this is an Extrinsic semiconductor. But I am having trouble finding the equation to use for this one. I would not use this correct:

    ni = BT^(3/2)*e(-Eg/2KT)

    If not Im stuck on the path im supposed to take. If anyone could lead me down the correct road itd be much appreciated!
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
  3. philliesws10

    Thread Starter New Member

    Mar 31, 2013
    5
    0
    Thank you for the quick reply! But why is this an intrinsic instead of an Extrinsic? Is it because it is not from group 3 or 5?
     
  4. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    It is an extrinsic semiconductor, you've added a dopant, but the mass action law relates the intrinsic carriers to an extrinsic (actually both), at thermal equilibrium.
     
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