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    Electronics Wednesday Sessions
       Session EL+MI-WeM

Paper EL+MI-WeM4
Epitaxial Growth of a Group IV Ferromagnetic Semiconductor: Mn@sub x@Ge@sub 1-x@

Wednesday, October 31, 2001, 9:20 am, Room 111

Session: Spintronics III: Ferromagnetic Semiconductors
Presenter: A.T. Hanbicki, Naval Research Laboratory
Authors: A.T. Hanbicki, Naval Research Laboratory
Y.D. Park, Naval Research Laboratory
A. Wilson, Naval Research Laboratory
G. Spanos, Naval Research Laboratory
B.T. Jonker, Naval Research Laboratory
Correspondent: Click to Email
Ferromagnetic semiconductors promise to provide spin-dependent functionality to the well-established technology of semiconductor device heterostructures. While much effort has focused on the III-Mn-V materials such as GaMnAs, where hole density is believed to play a critical role, the origins of ferromagnetic (FM) order remain elusive. This is due in part to complications arising from use of compound semiconductor hosts. Mean field calculations predict that FM order should be stabilized in many other semiconductor materials, if certain Mn concentrations and hole densities can be realized.@footnote 1@ We have chosen one of the simplest semiconductor hosts, Ge, in which to investigate and better understand such effects. We report here the epitaxial growth of the first Group IV ferromagnetic semiconductor, Mn@sub x@Ge@sub 1-x@, and describe the structural, magnetic, and magneto-transport properties. Single crystal films were grown for x < 0.1 on GaAs(001) and Ge(001) substrates by MBE at low substrate temperatures from elemental sources. RHEED and x-ray diffraction confirm crystallinity and orientation. Samples exhibit hysteretic M vs H loops with significant remanence, and coercivities of several hundred Gauss. Curie temperatures range from 30 to 120 K with increasing Mn concentration, as determined from SQUID magnetometry. Films exhibit a non-metallic temperature dependent resistivity, as well as a pronounced extraordinary Hall effect. They are strongly p-type with hole densities of 10@super 19@ - 10@super 20@ cm@super -3@. Gated structures confirm that the hole density can be varied. Results will be presented on efforts to toggle ferromagnetism by application of a gate voltage at temperatures significantly higher than recently reported for InM nAs.@footnote 2@ This work was supported by the DARPA SpinS program and ONR. @FootnoteText@ @footnote 1@ T. Dietl, et al., Science 287, 1019 (2000). @footnote 2@ H. Ohno et al, Nature 408, 944 (2000).