AVS 49th International Symposium
    Electronic Materials and Devices Monday Sessions
       Session EL+SC+MI-MoA

Paper EL+SC+MI-MoA4
A Schottky Tunnel Barrier Contact for Electrical Spin Injection into a Semiconductor

Monday, November 4, 2002, 3:00 pm, Room C-107

Session: Metal-Semiconductor Interfaces
Presenter: B.T. Jonker, Naval Research Laboratory
Authors: B.T. Jonker, Naval Research Laboratory
A.T. Hanbicki, Naval Research Laboratory
G. Kioseoglou, Naval Research Laboratory
G. Itskos, SUNY at Buffalo
R. Mallory, SUNY at Buffalo
A. Petrou, SUNY at Buffalo
Correspondent: Click to Email
Electrical injection of spin polarized electrons into a semiconductor heterostructure is a critical issue for semiconductor-based spintronic devices. While very encouraging results have been obtained using magnetic semiconductors as injecting contacts,@footnote 1@ the desire for room temperature operation at low magnetic fields leads one to consider other materials and avenues. Ferromagnetic (FM) metals offer high Curie temperatures and can be rapidly switched (~ 300 ps) at low applied fields. However, theory has indicated that only very small spin injection (~0.01%) can be expected for typical FM metals as diffusive contacts.@footnote 2@ We report here electrical spin injection from an Fe Schottky contact into an AlGaAs/GaAs LED structure, with spin injection efficiencies above 34% which extend to room temperature. These robust effects are attributed to spin tunneling@footnote 3@ through the tailored Schottky barrier contact. The samples are grown by MBE, and the width of the depletion region at the Fe/AlGaAs interface is controlled by the semiconductor doping profile. Under reverse bias, electrons tunnel from the Fe into the semiconductor, and radiatively recombine in the GaAs quantum well. The circular polarization of the surface emitted electroluminescence (Faraday geometry) provides a quantitative, model independent measure of the QW spin polarization, and hence the injection efficiency.@footnote 1@ The spin tunnel current is dominated by minority spin carriers, in contrast to previous work using Al@sub 2@O@sub 3@ tunnel barriers and a superconducting film detector. The temperature dependence of the polarization will also be discussed. These results will be compared with previous work@footnote 4@ and theoretical modeling of Schottky barrier injection. Work supported by the DARPA SpinS program and ONR. @FootnoteText@ @footnote 1@R. Fiederling, et al Nature (1999); B.T. Jonker et al, PRB (2000)@footnote 2@G. Schmidt et al, PRB (2000)@footnote 3@E.I. Rashba, PRB (2000)@footnote 4@H.J. Zhu et al, PRL (2001).