Question

In a pure semiconductor, the number of conduction electrons is $6\times {10}^{19}$ per cubic metre. How many holes are there in a sample of size $1cm\times 1cm\times 1mm?$

Answer 1

In a pure semiconductor, the number of conduction electrons = number of holes.

Given Volume

$=1cm\times 1cm\times 1mm$

$=1\times {10}^{-2}\times 1\times {10}^{-2}\times 1\times {10}^{-3}$

$={10}^{-7}{m}^3$

Number of electrons

$=6\times {10}^{13}\times {10}^{-7}=6\times {10}^{12}$

Hence number of holes

$=6\times {10}^{12}$