Electronic Transport Properties Of Nonuniform Ferromagnetic Semiconductor/Single Crystal Si Heterostructures

Spin-dependent electronic transport in ferromagnet/semiconductor (FM/SC) heterostructures hasbecome a hot topic because the manipulation of carrier spin in FM/SC heterostructures offers the enhancedfunctionality of spintronics devices. Spin injection into a nonmagnetic SC has been observed at lowtemperatures in ferromagnetic metal/nonmagnetic SC heterostructures. However, the relatively lowinjection efficiency still cannot satisfy the practical application. Thus, it is interesting to investigateelectronic transport properties of ferromagnet/semiconductor heterostructures.Ni-CNx/p-Si and TiCoO/p-Si heterostructures were fabricated using magnetronsputtering. Their chemical composition, microstructure, magnetic, electrical transportproperties were carried out a detailed characterization and analysis.By studying electronic transport properties of Ni-CNx/p-Si heterostructures,we get that:In the amorphous Ni–CNx/p-Si heterostructure, the positive MR in the reverse range can beattributed to the formation of a spin-polarized barrier, which is further confirmed by thetemperature-peak-type MR. In the forward range, a positive MR of~90%is observed, whichmay be related to the peak in the R–I curves around0.01mA at low temperatures.By studying magnetic, electronic transport properties of Ni-CNx/p-Si heterostructures,we get that:(1) The film has a clear hysteresis loop, coercivity is about1.0kOe at3K. At305K, the coercivity is zero. TiCoO layer of TiCoO/p-Si heterostructures is semiconducting.Below123K, the relationship between conductivity and temperature satisfies the equation ofσ=σ0exp[-(T0/T)1/4], which includes that the electric transport mechanism of the TiCoO layeris variable-range hopping between localized states of electrons.(2) TiCoO/p-Siheterostructures conduction mechanism is ohm conductivity at305K and the space chargelimited current (SCLC) transmission mechanism at20K. TiCoO/p-Si heterostructures do notapparent electron accumulation phenomenon, its MR varies with temperature in the both ofpositive and negative current regions have shown peaks.