Berlin 2005 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 23: Postersitzung I

DS 23.17: Poster

Freitag, 4. März 2005, 16:00–18:30, Poster TU B

Fabrication and characterization of modulation doped ZnO/Zn1-x MgxO:Al films — •Goetz Vollweiler, Klaus Ellmer, Thilo Glatzel und Ulrike Bloeck — Hahn Meitner Institut, Glienicker Str. 100, 14109 Berlin

ZnO/Zn1-xMgxO:Al multilayer films have been grown by magnetron sputtering on sapphire substrates with different orientations and on glass. With such modulation-doped multilayers we want to investigate if the carrier mobility of highly doped ZnO films, which is limited by ionized impurity scattering, can be increased. The thickness of the single layers has been varied from 3 to 200 nm. Crystallinity and orientation of the films were measured by X-ray diffraction. It has been proved that the multilayer films grow epitaxially on the single crystalline sapphire substrates. The modulation doping has been verified by secondary ion mass spectrometry, Kelvin force microscopy on cross sections and by transmission electron microscopy. Depending on the thickness of the single layers, we found specific resistances up to 2,2 · 10⁻³ Ωcm and mobilities up to 15 cm²/Vs. The electrical parameters do not show a strong correlation with the structural film quality. This we ascribe to the decisive role of oxygen which leads to an almost full oxidation of the zinc oxide films, due to their low thickness. Furthermore, the stress in the films, which is caused by the large lattice mismatch between zinc oxide and sapphire contributes to a reduced mobility in these films.