Defect profiles were determined, in proton-implanted lightly-doped (1014/cm3) n-type layers, by making positron-electron pair momentum-distribution measurements using a slow-positron beam, conventional positron lifetime and e+-e- pair momentum-distribution measurements with a 22Na source, and spreading resistance measurements. It was found that the predominant positron trap which was introduced by 1.15 and 3.0MeV proton implantation was the Si di-vacancy, V2. The di-vacancy was observed in the negative charge state, V2-. The di-vacancy profile was determined in n-type samples which had been implanted with 1.15MeV protons to a dose of 1014/cm2, and a maximum concentration of between 4 x 1015 and 8 x 1015/cm3 was observed at depths of 16 to 18. The resistivity increased with increasing di-vacancy concentration. After annealing at 400C, spreading resistance measurements revealed a region of shallow H-related donors at depths of 15 to 21. The positron annihilation results supported the idea that the introduction of shallow donors was due to the formation of H-vacancy complexes during annealing.

H.Kauppinen, C.Corbel, K.Skog, K.Saarinen, T.Laine, P.Hautojärvi, P.Desgardin, E.Ntsoenzok: Physical Review B, 1997, 55[15], 9598-608