Question

The resistivity of a uniformly doped n-type silicon sample is $0.5\Omega -cm$. If the electron mobility $\left({\mu }_n\right)$ is $1250c{m}^2/V-sec$ and the charge of an electron is $1.6\times {10}^{-19}$ Coulomb, the donor impurity concentration $\left(N_D\right)$ in the sample is

• A. $1\times {10}^{16}/c{m}^3$
• B. $2\times {10}^{15}/c{m}^3$
• C. $2\times {10}^{16}/c{m}^3$
• D. $2.5\times {10}^{15}/c{m}^3$

Answer 1

The correct option is A $1\times {10}^{16}/c{m}^3$

Ans : (b)

$\rho =\frac{1}{nq{\mu }_n}$
$n=N_D$
$N_D=\frac{1}{q{\mu }_n\rho }=\frac{1}{1.6\times {10}^{-19}\times 1250\times 0.5}$
$={10}^{16}/c{m}^3$