Pronounced magnetic-field- and bias-sensitive features of the transport properties of a Fe/SiO₂/p-Si hybrid structure in planar geometry at temperature variation are investigated. Comparative analysis of two Fe/SiO₂/p-Si samples, one with a continuous Fe film and the other with two electrodes formed from a Fe layer and separated by a micron gap, shows that these features are due to the metal-insulator-semiconductor (MIS) transition with a Schottky barrier near the interface between SiO₂ and p-Si. Resistance of such a MIS transition depends exponentially on temperature and bias. In the structure with a continuous ferromagnetic film, the competition between conductivities of the MIS transition and the Fe layer results in the effect of current channel switching between the Fe layer and a semiconductor substrate. Within certain limits, this process can be controlled by a bias current and a magnetic field. Positive magnetoresistance of the structures at high temperatures is determined, most likely, by disorder-induced weak localization. In the structure with the gap, negative magnetoresistance is observed at certain temperature and bias. Its occurrence should be attributed to an inversion layer formed in the semiconductor near the SiO₂/p-Si interface when MIS transition is in the inversion regime.

We report on abrupt changes in dc resistance and impedance of a diode with the Schottky barrier based on the Mn/SiO₂/p-Si structure in a magnetic field. It was observed that at low temperatures the dc and ac resistances of the device change by a factor of more than 10⁶ with an increase in a magnetic field to 200 mT. The strong effect of the magnetic field is observed only above the threshold forward bias across the diode. The ratios between ac and dc magnetoresistances can be tuned from almost zero to 10⁸% by varying the bias. To explain the diversity of magnetotransport phenomena observed in the Mn/SiO₂/p-Si structure, it is necessary to attract several mechanisms, which possibly work in different regions of the structure. The anomalously strong magnetotransport effects are attributed to the magnetic-field-dependent impact ionization in the bulk of a Si substrate. At the same time, the conditions for this process are specified by structure composition, which, in turn, affects the current through each structure region. The effect of magnetic field attributed to suppression of impact ionization via two mechanisms leads to an increase in the carrier energy required for initiation of impact ionization. The first mechanism is related to displacement of acceptor levels toward higher energies relative to the top of the valence band and the other mechanism is associated with the Lorentz forces affecting carrier trajectories between scatterings events. The estimated contributions of these two mechanisms are similar. The proposed structure is a good candidate for application in CMOS technology-compatible magnetic- and electric-field sensors and switching devices.

Spin accumulation effect in Fe ₃ Si/p-Si structure with low boron doped silicon substrate was found. Calculated spin lifetimes are comparable with results reported earlier but for structures with highly doped semiconductors (SC) with or without a tunnel barrier introduced between the SC and ferromagnet (FM). Electrical characterization of a prepared Fe ₃ Si/p-Si diode allowed the determination of possible reasons for the pronounced spin signal. Analysis of the forward bias I-V curve revealed a Schottky barrier at the Fe ₃ Si/p-Si interface with a height of ϕ B p = 0.57 eV . Then, using impedance spectroscopy, we observed interface states localized in the band gap of silicon with energy of E _LS = 40 meV. Such states most probably cause the observed spin signal. We believe that in our experiment, spin-dependent hole extraction was performed via the interface states resulting in the minority spin accumulation in the silicon valence band. The observed effect paves the way to the development of different spintronic devices based on FM/SC structures without dielectric tunneling barriers.