AVS 52nd International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI+EM-WeA

Paper MI+EM-WeA4
Epitaxial Growth of Ferromagnetic Mn@sub 3-delta@Ga Thin Films on Wurtzite GaN(0001) by Molecular Beam Epitaxy

Wednesday, November 2, 2005, 3:00 pm, Room 204

Session: Magnetic Semiconductors
Presenter: E.D. Lu, Ohio University
Authors: E.D. Lu, Ohio University
M.B. Haider, Ohio University
R. Yang, Ohio University
C. Constantin, Ohio University
G. Pokharel, Ohio University
D.C. Ingram, Ohio University
A.R. Smith, Ohio University
Correspondent: Click to Email
Magnetic metal and/or alloy films on III-V semiconductor substrates have attracted considerable interest due to the potential applications for magnetic/spintronic materials and devices,especially as spin electron injection sources for spin-sensitive heterostructures as well. The binary MnGa alloy is one of several promising metallic ferromagnetic candidates with CuAu-I type ordering. It is a face-centered tetragonal (fct) structure with lattice constants a = 3.897 Å, c = 3.58-3.65 Å dependent on content of at.% Mn between 55-60%. The epitaxial ferromagnetic Mn@sub 3-δ@Ga(111) thin films have been grown on wurtzite GaN(0001) substrates with Ga polar surface by molecular beam epitaxy through controlling the substrate temperature and flux ratio of manganese to gallium during the growth. Prior to growing Mn@sub 3-δ@Ga thin films, the commercial MOCVD GaN substrates were directly heated for clean up and refreshed by growth of GaN layer by radio plasma MBE. The growth and structure of the Mn@sub 3-δ@Ga thin films are monitored in situ by reflection high energy electron diffraction (RHEED). The RHEED pattern was spotty at the initial stage and gradually became streaky, indicating surface roughness at the beginning and finally a smoother surface at the end. Combined RHEED and ex situ XRD results have revealed the primarily structure of the CuAuâ?"I type fct Mn@sub 3-δ@Ga thin films grown with (111) plane lying on GaN(0001) plane; due to double lattice constant of the Mn@sub 3-δ@Ga(111) plane along [11-2] direction is a good match with that distance along [11-20] direction of GaN(0001) (less than 4% mismatch), the epitaxial relationship of the fct Mn@sub 3-δ@Ga is (111)[01-1] MnGa // (0001)[1-100]GaN and (111)[11-2] MnGa // (0001)[11-20]GaN. Rutherford Backscattering Spectroscopy (RBS) has also confirmed composition of the Mn@sub 3-δ@Ga thin films with the ratio of Mn to Ga about 1.5 to 1.