Deep levels which were related to Fe in n-type material were investigated by using thermally stimulated capacitance methods, combined with minority carrier injection. This revealed 2 traps: at Ev + 0.31 and Ev + 0.41eV. The trap at Ev + 0.41eV was a donor that was attributed to interstitial Fe. The trap at Ev + 0.31eV, attributed to a complex of interstitial Fe and H, was observed in samples which were chemically etched using a mixture which contained HF and HNO3. It annihilated after annealing (175C, 0.5h). It was demonstrated that interstitial 3d transition metals, such as V, Cr and Fe, tended to form complexes with H in n-type material, and the complexes introduced donor levels which were below the donor levels of the isolated interstitial species. This trend was attributed to interactions between metals and H in complexes.

T.Sadoh, K.Tsukamoto, A.Baba, D.Bai, A.Kenjo, T.Tsurushima, H.Mori, H.Nakashima: Journal of Applied Physics, 1997, 82[8], 3828-31