A method for forming a semiconductor device includes forming a III-V semiconductor substrate and forming a gate structure on the III-V semiconductor substrate. The method also includes forming a thin spacer surrounding the gate structure and forming a source/drain junction with a first doped III-V material at an upper surface of the III-V semiconductor substrate. The method also includes oxidizing a surface the source/drain forming an oxidation layer; removing natural oxides from the oxidation layer on a surface of the source/drain to expose ions of the first doped III-V material at least at a surface of the source/drain. The method further includes applying a second doping to the source/drain to increase a doping concentration of the first doped III-V material, forming metal contacts at least at the second doped surface of the source/drain; and then annealing the contact.