AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM+MI-TuA

Paper EM+MI-TuA4
Interface Structure and Spin Injection Efficiency in a Ferromagnetic/Semiconductor Spin-LED

Tuesday, November 1, 2005, 3:00 pm, Room 310

Session: Spin Injection
Presenter: A.T. Hanbicki, Naval Research Laboratory
Authors: A.T. Hanbicki, Naval Research Laboratory
G. Kioseoglou, Naval Research Laboratory
R. Goswami, Naval Research Laboratory
T.J. Zega, Naval Research Laboratory
O.M.J. van 't Erve, Naval Research Laboratory
C.H. Li, Naval Research Laboratory
R.M. Stroud, Naval Research Laboratory
G. Spanos, Naval Research Laboratory
B.T. Jonker, Naval Research Laboratory
Correspondent: Click to Email
Considerable effort has been made to incorporate ferromagnetic metals into semiconductor spintronic devices. The nature of the interface between a magnetic contact and a semiconductor is expected to influence the spin-injection efficiency. Indeed, we have discovered interface effects play a role in the spin-injection efficiency for an all-semiconductor system.@footnote 1@ Recently we demonstrated robust spin injection from Fe into an AlGaAs/GaAs spin-LED. With this system, we have successfully injected spin polarized electrons with an electron spin polarization of 32% in the GaAs quantum well (QW).@footnote 2@ To correlate the interface structure with the observed QW polarization, we have characterized our Fe/AlGaAs contacts using high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy, and high-angle annular-dark-field (HAADF) imaging. HRTEM together with HAADF imaging provides compositional information that can also be used to determine the interfacial character. We have studied several samples with different detector heterostructures. Optimized annealing can improve the measured spin polarization, therefore for each sample several pieces were annealed to generate a systematic dataset. Enhancement in polarization is seen with anneals as low as 175°C, and the maximum increase in polarization occurs for anneals above 200°C. Measured spin polarizations increase by 8 to 10%, independent of the starting value. Preliminary results reveal a correlation between the GaAs QW spin polarization and the thickness of the Fe/AlGaAs interface. As the interface thickness increases from 0.5 to 0.9 nm, the measured polarization decreases from 27% to 18%. There are also indications that the Fe film is affected by annealing and implications toward spin injection will be discussed. This work was supported by the DARPA SpinS program and ONR. @FootnoteText@ @footnote 1@R.M. Stroud, et al, PRL 89 (2002)@footnote 2@A.T. Hanbicki, et al, APL 82 (2003).