Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 28: Transport properties

HL 28.8: Vortrag

Dienstag, 26. Februar 2008, 11:15–11:30, ER 164

Electrical transport properties of GaGdN epitaxial layers — •Amilcar Bedoya Pinto, Martin Roever, Joerg Malindretos, and Angela Rizzi — IV. Physikalisches Institut and Virtual Institute of Spin Electronics (VISel), Georg-August Universität Göttingen, D-37077 Göttingen, Germany

In the last years, the rare-earth element Gd has gained great attention as a magnetic dopant in the wide-gap semiconductor GaN, due to the unexpected high magnetic moment per Gd-atom induced in the host matrix at very low Gd-concentrations. In the DMS theory, ferromagnetic coupling is often linked to electrical transport. However, less is known about the electrical transport properties in Gd-doped GaN. For this purpose, GaGdN layers (d=500nm) have been grown by MBE on semi-insulating 6H(0001) SiC substrates. We find that Gd-doping increases the resistivity up to four orders of magnitude compared to unintentionally doped GaN, showing a temperature dependence (T^−1/2) in the low temperature-range (<60K), which is characteristic of hopping conductivity in an impurity band of localized states in the gap. In order to find out whether this impurity band is created by the spin-splitted f-states of Gd or rather by structural defects, samples with different Gd concentrations are studied. In addition, transport properties of silicon co-doped samples might clarify whether carriers play a role in mediating the observed ferromagnetism in this material system.