The ratio of electron and hole currents in a semiconductor is $7 / 4$ and the ratio of drift velocit

Question

The ratio of electron and hole currents in a semiconductor is $7 / 4$ and the ratio of drift velocities of electrons and holes is $5 / 4$. Then ratio of concentrations of electrons and holes will be\

Professor PC Thomas Classes · Answer

(b) $I_{h}=n_{h} e A V_{d h} ; I_{e}=n_{e} A V_{d e}$ $$ \mathrm{n}_{\mathrm{h}}=\frac{\mathrm{I}_{\mathrm{h}}}{\mathrm{eAV}_{\mathrm{dh}}} ; \quad \mathrm{n}_{\mathrm{e}}=\frac{\mathrm{I}_{\mathrm{e}}}{\mathrm{eAV}_{\mathrm{de}}} $$ $\frac{\mathrm{n}_{\mathrm{e}}}{\mathrm{n}_{\mathrm{h}}}=\frac{\mathrm{I}_{\mathrm{e}}}{\mathrm{V}_{\mathrm{de}}} 	imes \frac{\mathrm{V}_{\mathrm{dh}}}{\mathrm{I}_{\mathrm{h}}}=\left(\frac{\mathrm{I}_{\mathrm{e}}}{\mathrm{I}_{\mathrm{h}}}ight)\left(\frac{\mathrm{V}_{\mathrm{dh}}}{\mathrm{V}_{\mathrm{de}}}ight)=\frac{7}{4} 	imes \frac{4}{5}=\frac{7}{5}$\