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I read in textbooks that the electric conductivity of a semiconductor is $\sigma=q(n\mu_n+p\mu_p)$, where $q$ is an electron's charge, $n$ and $p$ are the concentrations of electrons and holes, $\mu_n$ and $\mu_p$ are their mobilities. In an intrinsic semiconductor $n=p$ but $\mu_n$ may be different from $\mu_p$.

In descriptions of the Hall effect that I found (e.g., here) they show calculations for just one type of carriers, $n$, or $p$, assuming that the semiconductor is extrinsic, either $n$- or $p$-type, so that the corresponding charge carrier dominates.

How do they experimentally find $\mu_n$ and $\mu_p$ in an intrinsic semiconductor?

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  • $\begingroup$ Well, how much should mobilities change with doping levels? You can vary the doping over orders of magnitude, so it would be easy to tell. $\endgroup$
    – Jon Custer
    Commented Jan 10 at 14:41
  • $\begingroup$ @JonCuster E.g. the electron mobility of intrinsic Si at 300 K is 1350 cm^2/Vs while with donor doping concentration of 10^17 cm^-3 it is 700 cm^2/Vs. Another thing, say, they synthesized a novel semiconductor. How do they measure the mobility of its electrons and holes? Do they have to dope it? For that, they might need to design a doping process which could be different for that particular material than it were for known ones. Can't they do it without doping? $\endgroup$
    – Vladislav Gladkikh
    Commented Jan 18 at 1:55

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