Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Mobility of electrons and holes

  1. Jan 9, 2009 #1
    Calculate mobilities of electrons and holes (assuming equal) in grey tin, silicon and germanium. Calculate also the mobility that would be necessary for diamond to have an intrinsic conductivity of 10-12 S m-1 if the hole and electron mobilities were equal.

    [tex]\sigma[/tex] = Nc (e[tex]\mu[/tex]n*e[tex]\mu[/tex]p)exp(−Eg /2kT)

    [tex]\sigma[/tex]= 10-12
    e = 1.6*10 -19
    k = 1.38*10 -23
    T = 300K
    Nc = 2.5*1025
    Eg(tin) = 0.08
    Eg(silicon) = 1.11
    Eg(germanium) = 0.66

    For tin
    Rearrange to give:

    [tex]\mu[/tex]np = [tex]\sigma[/tex] / 2e Nc exp(−Eg /2kT)

    The exponential becomes equal to zero...

    I'm quite sure i'm missing something relatively simple here but not sure what
  2. jcsd
  3. Jan 9, 2009 #2
    It appears i was using wrong values for the conductivity and boltzmann constant, got the correct answer now.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook