AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI+SC-FrM

Invited Paper MI+SC-FrM3
Tunnel Spin Injection from a Ferromagnetic Metal into a Semiconductor Heterostructure

Friday, November 7, 2003, 9:00 am, Room 316

Session: Semiconductor Spin Injection
Presenter: A.T. Hanbicki, Naval Research Laboratory
Authors: A.T. Hanbicki, Naval Research Laboratory
O.M.J. van 't Erve, Naval Research Laboratory
R. Magno, Naval Research Laboratory
G. Kioseoglou, Naval Research Laboratory
C.H. Li, Naval Research Laboratory
R.M. Stroud, Naval Research Laboratory
B.T. Jonker, Naval Research Laboratory
G. Itskos, SUNY at Buffalo
R. Mallory, SUNY at Buffalo
M. Yasar, SUNY at Buffalo
A. Petrou, SUNY at Buffalo
Correspondent: Click to Email
Significant effort has been made to incorporate ferromagnetic metals into semiconductor spintronic devices because they offer high Curie temperatures, low coercive fields, and a ready source of spin polarized electrons. Recently it has been shown that the key to efficient spin injection from a metal into a semiconductor heterostructure is a sufficient interface resistance.@footnote 1@ Tunnel barriers have been a common way of satisfying this criterion, and there are a number of recent experimental successes with Schottky contacts, thin metal oxides, and AlAs. We will review the state of the art of spin injection from an Fe Schottky contact into an AlGaAs/GaAs spin-LED. A Schottky barrier at the Fe/AlGaAs interface can serve as an effective tunnel contact if the doping profile of the semiconductor near the interface is engineered to produce a narrow depletion width. In this system, we have successfully injected polarized electrons and obtained electron spin polarizations ranging from 13% to 32% in the GaAs QW,@footnote 2@ where quantum selection rules directly link the measured circular polarization and the electron spin population. We report here recent efforts to characterize transport properties and the physical structure of this interface, and correlate them with the measured spin polarizations. To determine the dominant transport mechanism, we have analyzed the transport process using the Rowell criteria. The parabolic G-V curves and the temperature dependence of the zero-bias resistance demonstrate that single step tunneling is the dominant transport mechanism. The I-V data show a clear zero-bias anomaly and phonon signatures providing further evidence for tunneling. Preliminary data suggest that roughness and Fe segregation at the spin injecting interface suppresses spin injection. @FootnoteText@ This work was supported by the DARPA SpinS program and ONR@footnote 1@E.I. Rashba, PRB 62 (2000)@footnote 2@A.T. Hanbicki, et al., APL 80 (2002); APL 82 (2003).