Question

In an intrinsic semiconductor, the density of conduction electrons is $7.07 \times 10^{15} \,m ^{-3} .$ When it is doped with indium, the density of holes becomes $5 \times 10^{22}\, m ^{-3}$. Find the density of conduction electrons in doped semiconductor

• A. Zero
• B. $1 \times 10^{9} \,m ^{-3}$
• C. $7 \times 10^{15}\, m ^{-3}$
• D. $5 \times 10^{22} \,m ^{-3}$

Answer 1

Answer: (B)

$n_{e} .n_{h}=n_{i}^{2}$
and $n_{e}=n_{h}=n_{i} $ initially
or $n_{i}=7.07 \times 10^{15} \,m ^{-3}$
$n_{e}=\frac{\left(7.07 \times 10^{15}\right)^{2}}{5 \times 10^{22}}$
on $n_{e} \approx 1 \times 10^{9}\, m ^{-3}$