Dresden 2011 – scientific programme

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DS: Fachverband Dünne Schichten

DS 43: Poster II: Thin Film Chalcogenide Photovoltaics; Thermoelectric Materials, Thin Films, and Nanostructures

DS 43.13: Poster

Wednesday, March 16, 2011, 15:00–17:30, P2

Thermal conductivity and thermoelectric properties of a suspended GaAs/AlGaAs heterostructure — •Matthias Schmidt, Andrea Stemmann, and Wolfgang Hansen — Institut für Angewandte Physik, Universität Hamburg, 20355 Hamburg, Germany

We study low-temperature magnetothermoelectric properties of two-dimensional electron systems (2DEGs) embedded in a thin suspended membrane consisting of a modulation doped GaAs/AlGaAs heterostructure grown by molecular beam epitaxy. Electron-beam lithography is used to pattern the top of the membrane featuring a micro-scaled Hall bar, thermometers, and a Joule heater on top. The heater at the central region of the membrane generates a strong thermal gradient between the hot and the cold end side of the 34 µm long Hall bar including the 2DEG. A temperature difference of more than 5 K can be achieved at a mean temperature well below 10 K. We present heat conductivity and magnetothermopower measurements. The results show that the specific thermal conductivity of the membrane is qualitatively and quantitatively different with respect to the bulk value. Observed magnetothermopower is similar to results of earlier publications on GaAs/AlGaAs heterostructures. However, in contrast to previous results our measurements of the zero-field thermopower reveal that thermodiffusion is the main source of the thermopower at temperatures up to 3 K until the phonon drag dominates the run of the thermopower. This value is significantly higher than reported for non-suspended heterostructures [1].
 [1] R. Fletcher et al., Phyical Review B 14991 (1994)