This work focuses on electrical characterisation of NiFe/SiO2/Si diodes that can be used as spin injection into silicon for future spintronic devices. Capacitance-voltage characteristics show a large increase of the Si/SiO2 interfacial state density compared to Al/SiO2/Si diodes. This result suggests that nickel and/or iron may have diffused across the SiO2 layer. Consistently the current-voltage experimental characteristics can be accounted for by using trap assisted electron transport mechanism. These traps may be attributed to ferromagnet atoms in the oxide bulk.