Eight new H-Co related deep levels in Co-doped material were reported. The traps formed after hydrogenation via wet chemical etching, mechanical polishing or hydrogenation in a H plasma. It was demonstrated that H and Co were necessary for the appearance of the new levels. The occurrence of Co passivation was observed in n-type samples after etching at room temperature. In p-type material, after annealing at 400K, new electrically active Co-H complexes occurred. One of these traps exhibited a fully reversible transition between the electrically active and electrically neutral configurations after heat treatment at temperatures of between 310 and 400K. All of the Co-H complexes annealed out at temperatures of between 400 and 600K, and the Co donors and acceptors were recovered.

W.Jost, J.Weber, H.Lemke: Materials Science Forum, 1995, 196-201, 927-32