  We achieved ohmic contacts down to 5 K on standard n-doped Ge samples by
creating a strongly doped thin Ge layer between the metallic contacts and the
Ge substrate. Thanks to the laser doping technique used, Gas Immersion Laser
Doping, we could attain extremely large doping levels above the solubility
limit, and thus reduce the metal/doped Ge contact resistance. We tested
independently the influence of the doping concentration and doped layer
thickness, and showed that the ohmic contact improves when increasing the
doping level and is not affected when changing the doped thickness.
Furthermore, we characterised the doped Ge/Ge contact, showing that at high
doping its contact resistance is the dominant contribution to the total contact
resistance.
