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

Paper EM+MI-TuA3
Characterization of Mn-based Contacts on GaAs

Tuesday, November 1, 2005, 2:40 pm, Room 310

Session: Spin Injection
Presenter: J.L. Hilton, University of Minnesota
Authors: J.L. Hilton, University of Minnesota
B.D. Schultz, University of Minnesota
S. McKernan, University of Minnesota
C. Adelmann, University of Minnesota
X. Lou, University of Minnesota
P.A. Crowell, University of Minnesota
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
Mn-based ferromagnetic materials, such as binary metals, Heusler alloys, diluted magnetic semiconductors, and digital alloys, are potentially useful as epitaxial spin injection contacts in GaAs-based spintronic devices. Defects and solid-state reactions at a ferromagnet/semiconductor interface have a significant influence on the spin injection efficiency of spintronic devices. Consequently, a detailed understanding of the interfacial interactions of Mn and Mn-based materials with GaAs is needed. In order to understand the thermodynamic phase behavior of the Mn-Ga-As ternary system, thin film Mn/GaAs structures were grown using molecular beam epitaxy. RHEED, LEED, STM, XPS, RBS, XRD, and cross-sectional TEM were used to characterize the Mn/GaAs interfacial reactions. These reactions initially resulted in the formation of a two-phase region of tetragonal Mn@sub 2@As and tetragonal @delta@-MnGa, with an average composition of Mn@sub 0.6@Ga@sub 0.2@As@sub 0.2@. The two phases formed an epitaxial lamellar layer on the GaAs substrate with Mn@sub 2@As(001)<100> and @delta@-MnGa(001)<100> // GaAs(001)<110>. Higher temperature anneals resulted in the dissociation of the Mn@sub 0.6@Ga@sub 0.2@As@sub 0.2@ region into a @delta@-MnGa layer near the sample surface and a Mn@sub 2@As layer near the GaAs substrate. Anneals of @delta@-MnGa films on GaAs suggest that @delta@-MnGa is thermodynamically stable in contact with GaAs over a narrow compositional range up to at least 400°C. For more Ga-rich Mn@sub 1-x@Ga@sub x@ films, no evidence of interfacial reactions with GaAs was observed, but there were significant structural changes within the film. Stable @delta@-MnGa films are especially desirable for use in spintronic devices due to their inherent perpendicular magnetization. Spin injection measurements utilizing @delta@-MnGa contacts on GaAs-based spin-LEDs will be presented. Supported by ARO, ONR, DARPA, NSF, and AFOSR.