Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 22: GaN: Pr
äparation und Charakterisierung I
HL 22.9: Talk
Saturday, March 5, 2005, 12:45–13:00, TU P-N201
Fermi level dependence of optical and magnetic properties in MOCVD-grown GaMnN — •Christoph Hums1,2, M. Strassburg2,3, M.H. Kane3, A. Asghar3, J. Senawiratne2, M. Alevli2, N. Dietz2, C.J. Summers3, I.T. Ferguson3, and A. Hoffmann1 — 1Technische Universität Berlin,Institut für Festkörperphysik, 10623 Berlin, Germany — 2Georgia State University, Department of Physics and Astronomy, Atlanta, GA 30302 — 3Georgia Institute of Technology, Electrical and Computer Engineering / Materials Science and Engineering, Atlanta, GA 30332
Transition metal (TM) doped wide gap semiconductors such as GaN and ZnO are revealed as the most promising candidates for room temperature spintronics applications. The ferromagnetic behavior strongly depends on the TM concentration and the prevailing carrier type. MOCVD grown GaMnN epilayers with varying Mn-concentration and Si co-doping have been studied. The effect on Mn incorporation on the formation of defect states and impurity subbands inside the bandgap in GaN was monitored by optical spectroscopy. A broad absorption band detected around 1.5 eV is attributed to the presence of a Mn-induced subband. The intensity of the absorption band correlates with the Mn concentration and vanishes upon silicon co-doping. The magnitude of magnetization decreases as the Fermi level is increased and crashes at Si concentrations of 1020 cm−3 . This strong Fermi level dependence of the magnetization can not result from phase segregation or ferromagnetic Mn-clusters.