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Is the following semiconductor n-type or p-type?

  1. May 17, 2016 #1
    1. The problem statement, all variables and given/known data

    Estimate the carrier density and mobility of a semiconductor with a Hall coefficient of ##R_{Hall} = 7*10^{-5} m^3C^{-1}## and a conductivity ##\sigma = 200 (\Omega m)^{-1}##. Is the semiconductor n-type or p-type?



    2. Relevant equations

    ##R_{Hall}=\frac{1}{ne}##
    ##\sigma=ne\mu_e + pe\mu_h##

    3. The attempt at a solution

    Given the request at hand, and going by many of the examples given in lectures, I figured the conductivity can be simplified to ##\sigma = 2ne\mu##, then from the given information I can use the ##R_{Hall}## equation to find ##n## then sub into the ##\sigma## equation and rearrange to find ##\mu##.

    Final answers:
    ##n = 8.1*10^{21} m^{-3}##
    ##\mu = 0.007 m^2/Vs##

    From this, how can I know if it's a p-type or n-type semiconductor? According to all the info I can find, the calculation I've just done is based on the assumption that I'm working with an intrinsic semiconductor which means it isn't n-type or p-type because ##n=p##. So I must be going wrong with the assumptions I've made in simplifying the calculation..? I'm not sure what I'm missing.

    Thanks.
     
  2. jcsd
  3. May 17, 2016 #2
    Ah, I've cracked it.

    The Hall coefficient is a positive value which means we're working with positive charge carriers. So it's p-type.

    Also I think this means I should not use the factor of 2 in the conductivity equation and simply use ##\sigma = pe\mu##
     
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