Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 16: GaN: Bauelemente

HL 16.2: Vortrag

Dienstag, 9. März 2004, 10:30–10:45, H13

Modification of GaN and AlGaN Surfaces for Nano- and Picofluidic Sensors — •G. Kittler, V. Cimalla, V. Lebedev, M. Fischer, V. Yanev, S. Krischok, J. A. Schaefer, and O. Ambacher — Technical University Ilmenau, Center for Micro- and Nanotechnologies, Gustav- Kirchhoff-Str. 1, D-98693 Ilmenau

Because of strong spontaneous polarization and piezoelectric coefficients of GaN layers and AlGaN/GaN-heterostructures free carrier concentration profiles inside these materials are very sensitive to any manipulation of surface charge. This physical effect can be used to develop novel sensors for ion fluxes, gases and polar liquids. We have used AlGaN/GaN-heterostructures with polarization induced two dimensional electron gases in order to determine volume, pH-value, or the polarity of water based nano- and picoliter droplets. To enable the determination of physical and chemical properties of such droplets a precise control of the droplet position on the active areas of the sensors is required. Firstly miscellaneous procedures of oxidation were used to optimize the wetting of the thin GaN-cap layers, and secondly thin structured hydrophobic layers were investigated for this purpose. For the latter method different materials e.g. silicon nitride, aluminum oxide, and fluorine-carbon-compounds were examined with respect to their hydrophobic properties. Effective procedures in controlling the wetting behavior of GaN and AlGaN surface were proven by Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), and contact-angle-measurements and will be presented in respect to the results obtained by electrical characterization of the first nanofluidic sensors.