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III-nitrides and compounds; iron impurity; intracenter transitions; spintronics
Abstract:
We report on optical studies of bulk GaN crystals doped with iron. High-quality freestanding GaN crystals with varying Fermi level position were grown using the hydride vapor phase epitaxy on bulk GaN substrates. Samples with the dominant neutral Fe3+(3d(5)) acceptor state showed a characteristic near-infrared luminescence band around 1.3 eV, consisting of several sharp lines due to the fine structure of the T-4(1)(G)-(6)A(1)(S) internal transitions of isolated Fe3+ (d(5)) ions. In a magnetic field, these lines split into several components. This allowed us to determine energy structure of the T-4(1), multiplet in the magnetic field. For samples containing a singly ionized Fe2+(3d(6)) acceptor, absorption due to well-resolved E-5-T-5(2) internal transitions of Fe2+ was observed. Measurements performed at different temperatures ranging from 7 to 50 K and at magnetic fields up to 13 T enabled us to analyze some sublevels of the E-5 ground and the T-5(2) excited state. (C) 2007 Elsevier B.V. All rights reserved.
