Article

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.

0 Bookmarks
 · 
113 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The growth and characterization of high-quality ultrathin Fe3O4 films on semiconductor substrates is a key step for spintronic devices. A stable, single-crystalline ultrathin Fe3O4 film on GaAs(001) substrate is obtained by post-growth annealing of epitaxial Fe film with thicknesses of 5 and 12 nm in air. Raman spectroscopy shows a high ability to convincingly characterize the stoichiometry, epitaxial orientation and strain of such ultrathin Fe3O4 films. Polarized Raman spectroscopy confirms the unit cell of Fe3O4 films is rotated by 45° to match that of the Fe (001) layer on GaAs, which results in a built-in strain of − 3.5% in Fe3O4 films. The phonon strain-shift coefficient(−126 cm−1) of the A1g mode is proposed to probe strain effect and strain relaxation of thin Fe3O4 films on substrates. It can be used to identify whether the Fe layer is fully oxidized to Fe3O4 or not. Copyright © 2011 John Wiley & Sons, Ltd.
    Journal of Raman Spectroscopy 06/2011; 42(6):1388-1391. · 2.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Binary information encoded within the spin of carriers can be transferred into corresponding right- or left-handed circularly polarized photons emitted from an active semiconductor medium via carrier-photon angular momentum conversion. In order to attain maximized spin injection at out-of-plane magnetic remanence, a number of material systems have been explored as possible solid-state spin injectors. However, the circular polarization (PC) of emitted light was still limited at 3–4% at remanence. Here, we demonstrate a sizable electroluminescence circular polarization from a III-V-based spin light-emitting diode at zero magnetic field with a perpendicular spin injector consisting of an ultrathin CoFeB ferromagnetic layer (1.2 nm) grown on a MgO tunnel barrier (2.5 nm). The maximum value of PC measured at zero field is as large as 20% at 25 K and still 8% at 300 K. These types of ultrathin perpendicular spin injectors are of great interest (i) to realize the electrical switching of the magnetization of the injector layer owing to the advanced spin-transfer torque properties of the CoFeB layer and (ii) to be directly embedded in optical cavities for spin lasers due to their very low optical absorption loss.
    Physical Review B 08/2014; 90:085310. · 3.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An efficient electrical spin injection into an InGaAs/GaAs quantum well light emitting diode is demonstrated thanks to a CoFeB/MgO spin injector. The textured MgO tunnel barrier is fabricated by two different techniques: sputtering and molecular beam epitaxy. The maximal spin injection efficiency is comparable for both methods. Additionally, the effect of annealing is also investigated for the two types of samples. Both samples show the same trend: an increase of the electroluminescence circular polarization (Pc) with the increase of annealing temperature, followed by a saturation of Pc beyond 350 °C annealing. Since the increase of Pc starts well below the crystallization temperature of the full CoFeB bulk layer, this trend could be mainly due to an improvement of chemical structure at the top CoFeB/MgO interface. This study reveals that the control of CoFeB/MgO interface is essential for an optimal spin injection into semiconductor.
    Applied Physics Letters 07/2014; 105(1):012404-012404-5. · 3.52 Impact Factor

Full-text (2 Sources)

Download
33 Downloads
Available from
May 20, 2014