Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 91: Poster Session: Spintronics / Magnetic Semiconductors / Transport
HL 91.17: Poster
Thursday, March 29, 2012, 16:00–19:00, Poster D
Hall effect in Cu-doped GaN films grown by molecular beam epitaxy — •Michael Maschek1, Philipp R. Ganz2, Christoph Sürgers1, Hilbert v. Löhneysen1,2, and Daniel M. Schaadt2,3 — 1Karlsruhe Institute of Technology, Physikalisches Institut, D-76049 Karlsruhe — 2Karlsruhe Institute of Technology, Center for Functional Nanostructures, D-76049 Karlsruhe — 3Institut für Energieforschung und Physikalische Technologien, TU Clausthal, D-38678 Clausthal-Zellerfeld
Group-III nitride semiconductors are attractive for spintronic device applications. A possible candidate for a nitride-based spin-aligner is Cu-doped GaN which exhibits ferromagnetic behavior at room-temperature, although Cu is an intrinsic non-magnetic material. However, the origin of the ferromagnetic behavior is not clear. Here we report on measurements of the Hall effect, resistivity, and magnetoresistance for temperatures T = 2 - 300 K and in magnetic fields up to 1 T performed on GaN:Cu films grown by plasma-assisted MBE. Films prepared under different growth conditions and of different thickness were investigated. With increasing Cu-to-Ga beam equivalent pressure (BEP) ratio the charge carrier density increases and the Hall mobility decreases due to defects introduced by Cu. Remarkably, samples with BEP ratio close to 1% show a strongly reduced charge carrier density and deviate from the general behavior. This suggests that Cu, which is preferentially substituted on Ga sites, acts as an acceptor up to a BEP ratio of 1%, whereas for higher concentrations Cu precipitates in Cu-Ga islands at the surface.