Q. A silicon specimen is made into a $p$-type semiconductor by doping, on an average, one indium atom per ${5 \times 10}^{7}$ silicon atoms. If the number density of atoms in the silicon specimen is ${5 \times 10}^{28}$ atoms $m^{- 3}$, then the number of acceptor atoms in silicon per cubic centimeter will be
A) ${2.5 \times 10}^{30}$ atom ${cm}^{- 3}$
B) ${2.5 \times 10}^{35}$ atom ${cm}^{- 3}$
C) ${1 \times 10}^{13}$ atom ${cm}^{- 3}$
D) ${1 \times 10}^{15}$ atom ${cm}^{- 3}$
Explanation
(d) Number density of atoms in silicon specimen
= ${5 \times 10}^{28}$ atoms-$m^{- 3} = {5 \times 10}^{22}$ atoms ${cm}^{- 3}$.
Since, 1 atom of indium is doped in ${5 \times 10}^{7}$ silicon atoms, so total number of indium atoms doped per ${cm}^{3}$ of silicon will be
$n = \frac{{5 \times 10}^{22}}{{5 \times 10}^{7}} = 10^{15}$ atom-${cm}^{- 3}$.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.