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HL: Halbleiterphysik

HL 43: GaN: Pr
äparation und Charakterisierung II

HL 43.3: Talk

Monday, March 7, 2005, 15:30–15:45, TU P164

MOCVD-grown GaMnN epilayers and nanostructures — •M. Strassburg^1,2, M.H. Kane^2,3, A. Asghar², Ch. Hums^1,4, 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.