The number of silicon atoms per m³ is 5 × 10²⁸. This is doped simultaneously with 5 × 10²² atoms per m³ of Arsenic and 5 × 10²⁰ per m³ atoms of Indium. Given that n_i= 1.5 × 10¹⁶ per m³.

$$\begin{gathered} \mathrm{Number} \mathrm{of} \mathrm{silicon} \mathrm{atoms}, \mathrm{N}=5\times {10}^{28} \\ \mathrm{Number} \mathrm{of} \mathrm{arsenic} \mathrm{atoms}, {\mathrm{n}}_{\mathrm{AS}}=5\times {10}^{22}\text{ atom }/{\mathrm{m}}^3 \\ \text{ Number of indium atoms, }{\mathrm{n}}_{\mathrm{IN}}=5\times {10}^{20}\text{ atom }/{\mathrm{m}}^3 \end{gathered}$$

${\mathrm{n}}_{\mathrm{i}}=1.5\times {10}^{16}\text{ electron }/{\mathrm{m}}^3$

$\Rightarrow {\mathrm{n}}_{\mathrm{e}}=5\times {10}^{22}-5\times {10}^{20}=4.95\times {10}^{22}$

Let number of holes be n_h​.

In thermal equilibrium, ${\mathrm{n}}_{\mathrm{e}}{\mathrm{n}}_{\mathrm{h}}={\mathrm{n}}_{\mathrm{i}}^2$

$\text{ so, }{\mathrm{n}}_{\mathrm{h}}=4.545\times {10}^9$

${\mathrm{n}}_{\mathrm{e}}>{\mathrm{n}}_{\mathrm{h}}, \mathrm{material} \mathrm{is} \mathrm{an} \mathrm{n}-\mathrm{type} \mathrm{semiconductor}.$