AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI+EL+SC-TuM

Paper MI+EL+SC-TuM9
Epitaxial Growth of the Diluted Magnetic Semiconductor Cr@sub x@Ge@sub 1-x@

Tuesday, November 5, 2002, 11:00 am, Room C-205

Session: Ferromagnetic Semiconductors
Presenter: G. Kioseoglou, Naval Research Laboratory
Authors: G. Kioseoglou, Naval Research Laboratory
A.T. Hanbicki, Naval Research Laboratory
Y.D. Park, Seoul National University, Korea
S.C. Erwin, Naval Research Laboratory
B.T. Jonker, Naval Research Laboratory
Correspondent: Click to Email
Ferromagnetic semiconductors (FMS) provide an opportunity to control spin-dependent behavior in semiconductor device heterostructures. Although much effort has focused on III-Mn-V materials such as GaMnAs , the mechanism of ferromagnetic order remains unclear; in particular the precise roles played by the dopant and the semiconductor host. We have explored this issue recently by developing a new Group-IV FMS, MnGe.@footnote 1@ Here we report our work to develop an elemental FMS using a different dopant, Cr-doped Ge. This choice was motivated partly by our density-functional theory (DFT) calculations, which indicate that CrGe and MnGe should have comparable Curie temperatures. We report the epitaxial growth of Cr@sub x@Ge@sub 1-x@ and describe the structural, magnetic and transport properties. The samples were grown on GaAs(001) substrates by molecular beam epitaxy at substrate temperatures of 40-500°C and the crystallinity was confirmed by the RHEED pattern. The Cr concentration used was 2-3% as determined from X-ray fluorescence. The RHEED pattern indicates single crystal growth for substrate temperatures above 200°C, with sharp 1x1 streaks. Growth at 40-70°C is initially single crystal, but the pattern becomes increasingly diffuse with film thickness. The samples are strongly p-type, and the hole density varies with the Cr concentration. SQUID measurements were performed on all samples to investigate the magnetic character of the Cr:Ge system. Samples grown at the higher growth temperatures exhibit only paramagnetic order. Co-doping with both Mn and Cr is also investigated. This work was supported by the DARPA SpinS program and ONR. @FootnoteText@ @footnote 1@Y.D. Park, et al., Science 295, 651 (2002).