Abstract
The potential use of Fe doped GaN for spintronics applications requires a complete understanding of the electronic structure of Fe in all of its charge states. To address these issues, a set of 500 µm thick freestanding HVPE grown GaN:Fe crystals with different Fe-concentration levels ranging from 5×1017 to 2×1020cm−3 was studied by means of photoluminescence, photoluminescence excitation (PLE) and Fourier transform infrared (FTIR) transmission experiments. The Fe3+/2+ charge transfer (CT) level was determined to be at 2.86 ± 0.01 eV above the valence band maximum considerably lower than the previously reported value of 3.17 ± 0.10 eV. A bound state of the form (Fe2+, hVB) with a binding energy of 50 ± 10 meV has been established as an excited state of Fe3+. FTIR transmission measurements revealed an internal (5E-5T2) transition of Fe2+ around 400 eV which, until now, was believed to be degenerate with the conduction band.
Consequently, a second CT band was detected in PLE spectra.
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Malguth, E., Hoffmann, A., Phillips, M. et al. Fe-Centers in GaN as Candidates for Spintronics Applications. MRS Online Proceedings Library 892, 505 (2005). https://doi.org/10.1557/PROC-0892-FF07-05-EE05-05
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DOI: https://doi.org/10.1557/PROC-0892-FF07-05-EE05-05