The electrical conductivity of pure germanium can be enhanced by

Pure germanium is an intrinsic semiconductor.

As temperature increases, thermal energy breaks covalent bonds, generating more electron-hole pairs. This increases the charge carrier density and enhances the electrical conductivity.

Doping pure germanium with donor impurities (pentavalent elements) provides free electrons, making it an n-type semiconductor and increasing its conductivity.

Doping with acceptor impurities (trivalent elements) creates holes, making it a p-type semiconductor and also increasing its conductivity.

Decreasing the temperature reduces the thermal generation of charge carriers, which decreases the conductivity.