Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 22: GaN: Pr
äparation und Charakterisierung I

HL 22.3: Talk

Saturday, March 5, 2005, 11:15–11:30, TU P-N201

Iron doped GaN as a potential material for spintronic devices — •Enno Malguth¹, A. Hoffmann¹, W. Gehlhoff¹, D. Azamat¹, O. Gelhausen², and M.R. Phillips² — ¹Institut für Festkörperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin — ²Microstructural Analysis Unit, University of Technology, Sydney, Australia

For the potential use of iron doped GaN as a material for spintronic applications it is of great importance to know the exact energetic position of the electronic states of the Fe ions in the bandgap. Another crucial issue is the charge state in which the iron is present. In order to investigate these issues a set of about 400 µ m thick freestanding HVPE grown GaN:Fe crystals with different Fe-concentration levels ranging from 2 × 10¹⁶ cm⁻³ to 2 × 10²⁰ cm⁻³ were studied by means of photoluminescence (PL), transmission, photoluminescence excitation (PLE) and electron paramagnetic resonance (EPR). The fact that the samples are freestanding permitted to carry out the optical experiments polarising parallel and perpendicular to the c-axis. Fe²⁺ , Fe³⁺ and Fe related defect-complexes were found to be present depending on the iron concentration. For the former two term schemes could be derived including fine structure. A multiple splitting of all these states due to the distortion of the trigonal crystal field along the c-axis in c_3v symmetry was observed. Particularly for the ⁵E → ⁵T₂ transitions of the Fe²⁺ which until now were believed to be degenerate with the conduction band a complex absorption structure could be resolved. Knowing the predominant polarisations of each transition line the exact splitting of the electronic Fe-states in the trigonal crystal field could be pinpointed.