Highly spin-polarized room-temperature tunnel injector for semiconductor spintronics using MgO(100).

IBM Research Division, Almaden Research Center, San Jose, California 95120, USA.
Physical Review Letters (Impact Factor: 7.73). 03/2005; 94(5):056601. DOI: 10.1103/PhysRevLett.94.056601
Source: PubMed

ABSTRACT The spin polarization of current injected into GaAs from a CoFe/MgO(100) tunnel injector is inferred from the electroluminescence polarization from GaAs/AlGaAs quantum well detectors. The polarization reaches 57% at 100 K and 47% at 290 K in a 5 T perpendicular magnetic field. Taking into account the field dependence of the luminescence polarization, the spin injection efficiency is at least 52% at 100 K, and 32% at 290 K. We find a nonmonotonic temperature dependence of the polarization which can be attributed to spin relaxation in the quantum well detectors.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the dependence of magnetoresistance effect on resistivity (rho) in Co/ZnO films deposited by magnetron sputtering at different sputtering pressures with different ZnO contents. The magnitude of the resistivity reflects different carrier transport regimes ranging from metallic to hopping behaviors. Large room-temperature magnetoresistance greater than 8% is obtained in the resistivity range from 0.08 to 0.5 [greek capital letter omega] . cm. The magnetoresistance value decreases markedly when the resistivity of the films is less than 0.08 [greek capital letter omega] . cm or greater than 0.5 [greek capital letter omega] . cm. When 0.08 [greek capital letter omega] . cm < rho < 0.5 [greek capital letter omega] . cm, the conduction contains two channels: the spin-dependent tunneling channel and the spin-independent second-order hopping (N = 2). The former gives rise to a high room-temperature magnetoresistance effect. When rho > 0.5 [greek capital letter omega] . cm, the spin-independent higher-order hopping (N > 2) comes into play and decreases the tunneling magnetoresistance value. For the samples with rho < 0.08 [greek capital letter omega] . cm, reduced magnetoresistance is mainly ascribed to the formation of percolation paths through interconnected elongated metallic Co particles. This observation is significant for the improvement of room-temperature magnetoresistance value for future spintronic devices.
    Nanoscale Research Letters 01/2014; 9(1):6. · 2.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have investigated the realizability of the controlled-NOT (CNOT) gate and characterized the gate operation by quantum process tomography for a chain of qubits, realized by electrons confined in self-assembled quantum dots embedded in the spin field-effect transistor. We have shown that the CNOT gate operation and its process tomography are performable by using the spin exchange interaction and several local qubit rotations within the coherence time of qubits. Moreover it is shown that when the fluctuation of operation time and the imperfection of polarization of channel electrons are considered as sources of decay of fidelity, the process fidelity of CNOT decreases at most 5% by the fluctuation of the operation time and its values of 0.49 and 0.72 are obtained for polarizations of the channel spin 0.6 and 0.8, respectively.
    The European Physical Journal B 09/2013; 86(9):393. · 1.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on the preparation of epitaxial MgO film on GaAs(001) substrates by molecular beam epitaxy at growth temperature of 20–200 °C. Reflection high energy electron diffraction, x-ray diffraction, and high resolution transmission electron microscopy reveal the growth of ordered crystalline cubic MgO(001) film at ∼200 °C with MgO(001)[100] || GaAs(001)[100] and a 4 : 3 lattice registry. The surface of the MgO films, characterized by atomic force microscopy, exhibits a root mean square roughness of only 0.5 nm. In situ stress measurements reveal tensile stress as low as 1.7 GPa for a growth temperature of 200 °C in good agreement with the calculated residual misfit strain.
    Journal of Applied Physics 10/2013; 114(15):154511. · 2.21 Impact Factor

Full-text (2 Sources)

Available from
May 20, 2014