Intrinsic Semiconductors

When pentavalent impurities are added to germanium, what type of semiconductor is obtained?

Distinguish between intrinsic seminconductor and extrinsic semiconductor

Pure silicon at $300 \mathrm{K}$ has equal electron and hole concentrations of $1.5\times {10}^{16} {\mathrm{m}}^{-3}.$ Doping by indium increases the hole concentration to $4.5\times {10}^{22} {\mathrm{m}}^{-3}.$ Calculate the new electron concentration in the doped silicon.

The resistivity of pure germanium at a particular temperature is $0.52 \mathrm{\Omega }\mathrm{m}.$ If the material is doped with ${10}^{20}$ atoms per ${\mathrm{m}}^{-3}$ of a trivalent impurity material, determine the new resistivity. The electron and hole mobilities are given to be $0.2 {\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ and $0.4 {\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ respectively. Take $e = 1.6\times {10}^{-19} \mathrm{C}$.

Mobilities of electrons and holes in a sample of intrinsic germanium at room temperature are $0.54 {\mathrm{m}}^2{\mathrm{v}}^{-1}{\mathrm{s}}^{-1}$ and $0.18 {\mathrm{m}}^2{\mathrm{v}}^{-1}{\mathrm{s}}^{-1}$ respectively. If the electron and hole densities are equal to $3.6\times {10}^{19} {\mathrm{m}}^{-3}$, calculate the germanium conductivity. Take, $e = 1.6\times {10}^{-19} \mathrm{C}$