Question

The number of silicon atoms per $m^3$ is $5\times {10}^{28}$. This is doped simultaneously with $5\times {10}^{22}$ atoms per $m^3$ of arsenic and $5\times {10}^{20}$ per $m^3$ atoms of indium. Calculate the number of electrons and holes. Given that $n_i=1.5\times {10}^{16}/m^3$. Is the material n-type or p-type?

Answer 1

Number of silicon atoms, $N=5\times {10}^{28}atom/m^3$

Number of arsenic atoms, $n_{AS}=5\times {10}^{22}atom/m^3$

Number of indium atoms, $n_{IN}=5\times {10}^{22}atom/m^3$

$n_i=1.5\times {10}^{16}electron/m^3$

$n_e=5\times {10}^{22}-1.5\times {10}^6=4.99\times {10}^{22}$

Let number of holes be $n_h$

In thermal equilibrium, $n_e{n}_h=n_i^2$

so, $n_h=4.51\times {10}^9$

$n_e>n_H$, material is an n-type semiconductor.