Question

Mobilities of electrons and holes in a sample of intrinsic Ge at room temperature are $0.35m^2/V-s$ and $0.18m^2/V-s$ respectively. If the electron and hole densities are each equal to $2.5\times {10}^{19}/m^3$, the Ge conductivity will be

• A. $3.12S/m$
• B. $2.12S/m$
• C. $1.12S/m$
• D. $4.12S/m$

Answer 1

The correct option is B $2.12S/m$

Conductivity of Ge
$\sigma =e(n_e{\mu }_e+nh{\mu }_h)$
Here $n_e=n_h=2.5\times {10}^{19}{m}^3$
$e=1.6\times {10}^{-19}$
$(2.5\times {10}^{19}\times 0.35+2.5\times {10}^{19}\times 0.18)$
$=1.6\times {10}^{-19}\times 2.5\times {10}^{19}\times 0.53$
$=2.12S/m$