We report the observation of a structurally induced doping compensation mechanism in doped semiconductor nanowires that results from the reduced size geometry. This kind of compensation can significantly affect the electronic transport properties of the doped nanowires. We demonstrate that in a crystalline n-type doped Ge wire, compensated by the acceptor-like localized surface states, strong electron-electron interactions occur. Variable range hopping conduction detected in these nanowires is directly generated from strong interactions, exhibiting an unusual large Coulomb gap in the density of states of wires. Published by AIP Publishing.