Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 43: GaN: Pr
äparation und Charakterisierung II
HL 43.3: Vortrag
Montag, 7. März 2005, 15:30–15:45, TU P164
MOCVD-grown GaMnN epilayers and nanostructures — •M. Strassburg1,2, M.H. Kane2,3, A. Asghar2, Ch. Hums1,4, J. Senawiratne1, M. Alevli1, N. Dietz1, C.J. Summers3, I.T. Ferguson2, U. Haboeck4, A. Hoffmann4, D. Azamat4, and W. Gehlhoff4 — 1Georgia State University, Department of Physics and Astronomy, Atlanta, GA 30302 — 2Georgia Institute of Technology, Electrical and Computer Engineering, Atlanta, GA 30332 — 3Georgia Institute of Technology, Materials Science and Engineering, Atlanta, GA 30332 — 4Technische Universität Berlin, Institut für Festkörperphysik, D - 10623 Berlin
High-quality GaMnN epilayers and nanostructures providing room temperature (RT) ferromagnetism were achieved. The incorporation of up to 2-5 % of Mn was enabled without significant drop in the crystalline quality taking advantage of MOCVD growth. Structural quality and absence of second phases were confirmed by high-resolution XRD, AFM and Raman spectroscopy. Local coordination and environment, and the valence state of the magnetic dopants were identified by electron paramagnetic resonance (EPR). Direct correlation of the Mn induced midgap-band with the magnetization was observed. Using co-doping (Si, Mg), the RT magnetization were explored in MOCVD-grown n- and p-type GaMnN epilayers. Strong Fermi level dependence of the magnetization was observed until the complete loss of ferromagnetic behavior for Silicon concentrations of 1020 cm−3. Hence, phase segregation or ferromagnetic clusters were ruled out to cause the observed ferromagnetism.