AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA2
Growth Characteristics of ErAs Interlayers in Metal/Ga@sub 1-x@Al@sub x@As Heterostructures

Tuesday, November 4, 2003, 2:20 pm, Room 327

Session: Surfaces and Interfaces of Semiconductors and Compound Materials
Presenter: B.D. Schultz, University of Minnesota
Authors: B.D. Schultz, University of Minnesota
J.L. Hilton, University of Minnesota
K. Lüdge, Technische Universität Berlin, Germany
C.J. Palmstrom, University of Minnesota
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Properties of thin-film metal contacts grown on GaAs substrates have long been explored for electronic device applications. For modern spintronic applications, control of the interfacial properties and the reactions between ferromagnetic metals and semiconductors is important for optimizing spin dependent transport across these interfaces. ErAs interlayers, as thin as 5ML, have been used as diffusion barriers to drastically reduce interfacial reactions between Fe@sub 1-x@Co@sub x@ and GaAs for growth temperatures up to 225°C. However, surface segregation of both Ga and As are observed during the Fe@sub 1-x@Co@sub x@ growth and are related to the growth characteristics of the ErAs interlayer. In-situ scanning tunneling microscopy (STM) studies of ErAs films grown by molecular beam epitaxy (MBE) at 535°C show that ErAs initially nucleates as 3-4 monolayer high islands embedded within, rather than on top of, the GaAs(100) surface. These islands grow laterally in size until a complete uniform film is formed, whereby additional growth occurs in a layer-by-layer mode. X-ray photoemission spectroscopy (XPS) reveals both the presence of Ga and As atoms on the ErAs surface following the formation of a continuous layer and the continued segregation of these atoms to the surface during growth. The excess As atoms dissociate from the ErAs surface upon post-growth anneals above 450°C, and STM images show additional ordering of the ErAs surface following these anneals. Growth of ErAs on AlAs(200Å)/GaAs(100) heterostructures eliminates the segregation of Ga to the ErAs surface and results in no surface segregation of Al atoms. This paper reports on the control of the growth modes and the surface composition of ErAs interlayers grown by MBE on Ga@sub 1-x@Al@sub x@As(100) surfaces as characterized in-situ by reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED), STM, and XPS. Supported by ONR, DARPA, and NSF.