Mobility of electrons in a semiconductor is defined as the ratio of their drift velocity to the applied electric field.

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Mobility of electrons in a semiconductor is defined as the ratio of their drift velocity to the applied electric field. If, for an n-type semiconductor, the density of electrons is 1019m–3 and their mobility is 1.6 m2/(V.s) then the resistivity of the semiconductor (since it is an n-type semiconductor contribution of holes is ignored) is close to:

(1) 2$Ω$m

(2) 0.4$Ω$m

(3) 4$Ω$m

(4) 0.2$Ω$m

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Ans: (2) 0.4$\Omega$m

Sol: $j = \sigma E = nev_d$

$\sigma=ne{v_d\over E}$

$=ne\mu$

${1\over\sigma}=\rho={1\over n_ee\mu_e}$

$={1\over10^{19}\times1.6\times10^{-19}\times1.6}$

$=0.4\Omega m$