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HL: Halbleiterphysik

HL 44: Poster II

HL 44.3: Poster

Donnerstag, 11. März 2004, 16:30–19:00, Poster A

Tunneling Through Single-Crystal GaAs(001) Barriers — •Marcus Zenger, Jürgen Moser, Peifeng Chen, Stephan Kreuzer, Werner Wegscheider, and Dieter Weiss — Universität Regensburg

We investigate transport through epitaxial GaAs(001) barriers (6-10 nm) sandwiched between evaporated polycrystalline metal films. To realize a metal/GaAs(001)/metal sandwich we use the epoxy-bond-and-stop-etch-technique. Previous experiments have shown a non-linear I-V-characteristic and a small but clear TMR ratio of 0.2-0.5%. To increase the TMR ratio we reduced the temperatures during the fabrication process. This leads to a higher TMR ratio of about 1.7% which corresponds to a polarization of about 9% in the Julliére model. A negative MR which is observed at high magnetic fields together with the still low degree of polarization suggests that spin-flip scattering is important at the Fe/GaAs interface. The negative MR in Fe/GaAs/Fe junctions will be compared to the corresponding high-field MR of nonmagnetic sandwiches, which grows quadratically. If this nearly temperature independent positive contribution is subtracted from our high-field TMR data a linear negative MR results. The latter seems to contain information about the spin-flip scattering process.