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Homework Help: Space charge width pn junction

  1. Jun 10, 2013 #1
    1. The problem statement, all variables and given/known data

    Calculate the width of the space charge region in a pn junction when a reverse biased voltage is applied. Consider a silicon pn junction at T=300K with doping concentrations of Na=10^16 cm^-3 and Nd=10^15 cm-3. Assume that Ni=1.5*10^10 cm-3 and VR=5V

    2. Relevant equations
    W=((2Ef(Vbi+Vr)/e)((Na+Nd)/((Na*Nd))))^1/2


    3. The attempt at a solution

    I correctly calculated the in built potential to be 0.635V however, I do not know how to calculate the fermi energy
     
  2. jcsd
  3. Jun 11, 2013 #2

    phyzguy

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    Science Advisor

    Check that formula again. It does not involve the Fermi energy.
     
  4. Jun 11, 2013 #3
    What is the value of epsilon in the formula attached?
     

    Attached Files:

  5. Jun 11, 2013 #4

    marcusl

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    Science Advisor
    Gold Member

    It's the permittivity of the material.
     
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