The migration of H was much higher in p-type than in n-type samples. It was concluded that H was a deep donor in this material.

E.M.Omeljanovsky, A.V.Pakhomov, A.Y.Polyakov, O.M.Borodina, E.A.Kozhukhova, A.Y.Nashelskii, S.V.Yakobson, V.V.Novikova: Solid State Communications, 1989, 72[5], 409-11