Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 3: Magnetic Semiconductors
MA 3.10: Vortrag
Montag, 25. Februar 2008, 12:30–12:45, H 1012
Hydrogen in GaN:Mn — •Christoph Bihler, Tobias Graf, Mario Gjukic, Moritz Hauf, Martin Stutzmann, and Martin S. Brandt — Walter Schottky Institut, Technische Universität München, Garching, Germany
Post-growth hydrogenation is known to switch the ferromagnetic semiconductors GaAs:Mn and GaP:Mn from their ferromagnetic to a paramagnetic state via passivation of Mn acceptors. In the wide-bandgap material GaN, the Mn2+/3+ charge transfer level is too deep for Mn to lead to effective p-type doping. Rather, a combination of optical absorption spectroscopy, elastic recoil detection and electron spin resonance (ESR) has led to the conclusion that Mn is predominantly in the 3+ oxidation state in this material. Nevertheless, a similar change of the oxidation state to 2+ by hydrogenation is expected, as found for GaAs:Mn and GaP:Mn. GaN:Mn with [Mn] ≈ 1020 cm−3 was subjected to hydrogenation in a remote DC hydrogen plasma for 2 hours at temperatures above 500∘C. We find that the ESR signal intensity of substitutional Mn2+ is increased by a factor of about 3 after this treatment. Moreover, hydrogenated samples exhibit further anisotropic hyperfine-split ESR lines which can be explained via additional uniaxial crystal field contributions along the different Ga-N bond axes in the spin Hamiltonian. The latter are attributed to local lattice distortions caused by the formation of Mn-H complexes with the hydrogen atom incorporated in a bond-centred or back bonded position. The changes in the ESR spectra upon hydrogenation can be reversed via annealing for 1 hour at temperatures above 600∘C.