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

  • Thread starter sa1988
  • Start date
  • #1
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Homework Statement



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?



Homework Equations



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

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.
 

Answers and Replies

  • #2
214
21
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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