\(\sigma=\mathrm{e}\left(n_{e} \mu_{e}+n h \mu_{h}\right)\)

Here \(n_{e}=n_{h}=2.5 \times 10^{19}\, / \mathrm{m}^{3}\)

\(e=1.6 \times 10^{-19} \,\mathrm{C}\)

\(\mu_{e}=0.35\, \mathrm{m}^{2} / \mathrm{V}-\mathrm{s}, \mu_{h}=0.18\, \mathrm{m}^{2} / \mathrm{V}-\mathrm{s}\)

\(\therefore \sigma=1.6 \times 10^{-19}\)

\(\left(2.5 \times 10^{19} \times 0.35+2.5 \times 10^{19} \times 0.18\right)\)

\(=1.6 \times 10^{-19} \times 2.5 \times 10^{19} \times 0.53\)

\(=2.12 \,\mathrm{S} / \mathrm{m}\)