By means of two-point-probe Spreading Resistance (SR) analyses, the formation and evolution of hydrogen-related and vacancy-related donor and acceptor states were studied in helium implanted and subsequently hydrogen plasma-treated n-type Float-Zone (FZ) silicon wafers. He-implantation was carried out at 3.75 MeV, applying fluences of 1×1014 cm-2 and 2×1013 cm-2. After 15-min post-implantation H-plasma exposures at substrate temperatures between 350 °C and 500 °C, distinct surplus doping profiles were observed in the subsurface layers of the treated FZ Si samples down to about 20 μm depth. Enhanced donor concentrations could be observed as well acceptor-like states, at least partially compensating for the initial n-type doping, so that even buried p-type layers can be created under appropriate process conditions. The nature of the defect complexes that were responsible for the observed doping profiles in the subsurface layer of the studied samples will be discussed.