Deep levels related to iron inn-type silicon have been investigated using thermally stimulated capacitance (TSCAP) combined with minority carrier injection. The TSCAP measurement reveals two traps ofEV+0.31andEV+0.41eV. The trap ofEV+0.41 eV is a donor due to interstitial iron. The trap ofEV+0.31eV, due to a complex of interstitial iron and hydrogen, is observed in the sample etched chemically with an acid mixture containing HF and HNO3and annihilates after annealing at 175 °C for 30 min. It is demonstrated that interstitial3dtransition metals such as vanadium, chromium, and iron tend to form complexes with hydrogen inn-type silicon, and the complexes induce donor levels below the donor levels of the isolated interstitial species. This trend is related to the interaction between the metals and hydrogen in the complexes. ©1997 American Institute of Physics.