Highly Spin-Polarized Room-Temperature Tunnel Injector for Semiconductor Spintronics using MgO(100)

Solid State and Photonics Laboratory, Stanford University, Palo Alto, California, United States
Physical Review Letters (Impact Factor: 7.51). 03/2005; 94(5):056601. DOI: 10.1103/PhysRevLett.94.056601
Source: PubMed


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.

Download full-text


Available from: James S Harris, Dec 31, 2013
  • Source
    • "The first one is to use a quarter-wave plate. The second possibility is based on the electrical injection of spin-polarized carriers into the active region [1] [2] [3] [4] [5] [6]. The third possibility is to modify the local electromagnetic field, for example, using chiral liquid crystals [7] [8] [9]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate theoretically the polarization properties of the quantum dot's optical emission from chiral photonic crystal structures made of achiral materials in the absence of external magnetic field at room temperature. The mirror symmetry of the local electromagnetic field is broken in this system due to the decreased symmetry of the chiral modulated layer. As a result, the radiation of randomly polarized quantum dots normal to the structure becomes partially circularly polarized. The sign and degree of circular polarization are determined by the geometry of the chiral modulated structure and depend on the radiation frequency. A degree of circular polarization up to 99% can be achieved for randomly distributed quantum dots, and can be close to 100% for some single quantum dots.
    Full-text · Article · Dec 2014 · Optics Letters
  • Source
    • "Thus, further material optimization is required to ensure perfect vertical alignment of the ferromagnetic contacts in remanence. Then, it can be expected that this efficiency can be increased up to about 30% combining the vertically magnetized ferromagnetic contacts with the optimized injector structure of Jiang et al. [8]. Thus, from the actual point of view, the optimum room-temperature spin-LED would look like it is schematically shown in Figure 3. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We discuss the concept of spin-controlled vertical-cavity surface-emitting lasers (VCSELs) and analyze it with respect to potential room-temperature applications in spin-optoelectronic devices. Spin-optoelectronics is based on the optical selection rules as they provide a direct connection between the spin polarization of the recombining carriers and the circular polarization of the emitted photons. By means of optical excitation and numerical simulations we show that spin-controlled VCSELs promise to have superior properties to conventional devices such as threshold reduction, spin control of the emission, or even much faster dynamics. Possible concepts for room-temperature electrical spin injection without large external magnetic fields are summarized, and the progress on the field of purely electrically pumped spin-VCSELs is reviewed.
    Full-text · Article · Mar 2012 · Advances in Optical Technologies
  • Source
    • "For samples capped with Au and at 7.1 to 28 ML, the uniaxial anisotropy is clearly visible and coexists with a four-fold cubic magnetocrystalline anisotropy. Its global easy axis is along [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] while [010] and [001] directions are equally magnetic hard. Such orientation of the easy and hard axes can also be found in the MgO capped samples within the same range. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Magnetic anisotropies of Fe/MgO/GaAs(100) hybrid structure with two different nonmagnetic capping materials, Au and MgO have been studied by ferromagnetic resonance (FMR). A uniaxial anisotropy, unexpected from the crystal structure was observed in the ultrathin films for both capping materials. Its global easy axis is along [0-11] direction while two (010) directions are equally magnetic hard regardless of the overlayer material. The in-plane uniaxial anisotropy (in-plane cubic anisotropy) of the Au capped samples is stronger (weaker) than that of the MgO capped ones within the range of t <sub>Fe</sub> = 7.1 to 28 ML. This suggests that the MgO overlayer suppresses the uniaxial anisotropy faster than the Au overlayer.
    Full-text · Article · Dec 2008 · IEEE Transactions on Magnetics
Show more