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MA: Fachverband Magnetismus

MA 33: Poster II

MA 33.7: Poster

Freitag, 26. März 2010, 11:00–14:00, Poster B1

Electronic localization and variable-range-hopping transport in GaMnN and GaGdN epitaxial layers — •Amilcar Bedoya-Pinto, Martin Roever, Dong-Du Mai, Joerg Malindretos, and Angela Rizzi — IV. Physikalisches Institut, Georg-August-Universität Göttingen, Germany

The interplay between magnetic and transport phenomena has been found to be a key issue to understand the origin of ferromagnetic coupling in dilute magnetic semiconductors (DMSs), as in the case of GaMnAs. Regarding III-V nitride DMSs, while there is a considerable number of reports based on magnetometry, only a few studies are devoted to the electrical transport behavior. In this sense, GaMnN and GaGdN epitaxial layers have been grown by molecular-beam epitaxy on both 6H-SiC and GaN:C highly-resistive substrates. Magnetic characterization was performed by SQUID-magnetometry. Temperature-dependent resistivity measurements of GaMnN layers show a transition from n-type activated transport to variable-range-hopping (VRH) as the Mn-concentration is increased. Regarding GaGdN layers, on the other hand, the observation of VRH-transport at low Gd-concentrations (∼ 10¹⁶cm⁻³) and the evaluation of the inferred hopping parameters suggest that not Gd itself, but Gd-induced defect states are the effective source for electronic localization. In both cases, the relation between magnetic and electrical transport properties is discussed taking into account the well-established models of ferromagnetic coupling in DMSs, as well as recent models proposing defect-induced magnetism in wide band-gap III-Nitrides.