AVS 50th International Symposium
    Semiconductors Thursday Sessions
       Session SC+MI-ThA

Paper SC+MI-ThA5
Thin Film Mn/GaAs(100) Interfacial Reactions

Thursday, November 6, 2003, 3:20 pm, Room 321/322

Session: Ferromagnetic and Dilute Magnetic Semiconductors
Presenter: J.L. Hilton, University of Minnesota
Authors: J.L. Hilton, University of Minnesota
B.D. Schultz, University of Minnesota
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
Although a number of ferromagnetic Mn-based compounds have been epitaxially grown on GaAs, there is a lack of detailed understanding of the interfacial interactions and their effects on spin transport. To date, no detailed Mn/GaAs interfacial reaction studies have been reported. In this study, the interfacial reactions of Mn thin films deposited in-situ on molecular beam epitaxy (MBE)-grown GaAs(100) epilayers are studied. Initial studies involved characterization of ex-situ post-growth anneals of Al(50Å)/Mn(2000Å)/GaAs(100) structures at temperatures of 200, 300, 350, 400, and 500°C for times ranging from 1-30 hours. Prior to annealing, the Mn films on GaAs appear from reflection high-energy electron diffraction and x-ray diffraction (XRD) to be polycrystalline, and Rutherford backscattering (RBS) indicates that no extensive interfacial reactions occur during growth. After annealing at temperatures higher than 200°C, XRD diffraction peaks corresponding to a tetragonal Mn@sub 2@As-like phase and a tetragonal MnGa-like phase are observed. RBS data at both normal and grazing geometries indicate significant Mn-Ga-As reactions occur during anneals in excess of 200°C with the formation of a region with Mn@sub 0.6@Ga@sub 0.2@As@sub 0.2@ composition. Higher temperature anneals result in the dissociation of this region into a MnGa-like region near the sample surface and a Mn@sub 2@As-like region near the GaAs substrate. RBS measurements of the reaction layer thickness for various annealing times at 300°C indicate the interfacial reactions are diffusion controlled. Results from RBS, XRD, and transmission electron microscopy of Al/Mn/GaAs structures will be combined with results from in-situ scanning tunneling microscopy and x-ray photoelectron spectroscopy of 0-20 monolayer Mn coverage studies to determine the nature and behavior of the reactions between Mn, Ga, and As at the metal-semiconductor interface. Supported by ONR, DARPA, and NSF.