Q. A silicon specimen is made into a $p$-type semiconductor by dropping, 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) $2.5 \times 10^{30}\ atoms\ cm^{- 3}$
B) $2.5 \times 10^{35}\ atoms\ cm^{- 3}$
C) $1.0 \times 10^{13}\ atoms\ cm^{- 3}$
D) $1.0 \times 10^{15}\ atoms\ cm^{- 3}$
Explanation
(d) Number density of atoms in silicon specimen $= 5 \times 10^{28}$ atoms/$m^{2} = 5 \times 10^{7}$ silicon atoms, so total number of indium atoms doped per atoms, so total number of indium atoms doped per $cm^{3}$ of silicon will be
$n = 5 \times 10^{22}/5 \times 10^{7} = 10^{15}$ atoms $cm^{- 3}.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.