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HL: Halbleiterphysik
HL 16: Poster Ia
HL 16.21: Poster
Freitag, 4. März 2005, 16:30–19:00, Poster TU E
Ballistic transport in nanoscale Si/SiGe cross-bars — •Sorin Poenariu1, Ulrich Wieser1, Ulrich Kunze1, and Thomas Hackbarth2 — 1Lehrstuhl für Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum — 2DaimlerChrysler Forschungszentrum Ulm, Wilhelm-Runge-Strasse 11, D-89081 Ulm
Starting from a high-mobility modulation-doped Si/SiGe heterostructure we prepare nanoscale field effect devices in order to study ballistic transport phenomena at T= 4.2 K. The transport channel is defined by a four-terminal ballistic cross-bar. Different symmetric and asymmetric geometries are realized with respect to the width and length of the current leads. We use a mix-and-match process which combines high resolution electron-beam lithography with calixarene and optical lithography with standard photoresist. The resulting resist pattern is transferred into the heterostructure by a low-damage CF4/O2 plasma process. For small current injection the four-terminal I-V-characteristic shows a negative bend resistance due to the ballistic motion of electrons. The influence of a top gate voltage on the I-V-characteristic is analyzed for different geometries. A second evidence of ballistic transport is a pronounced negative differential conductance (NDC) which is found in two-terminal I-V-characteristics of cross-bars and quasi one-dimensional wires. This NDC is attributed to phonon emission of electrons in the hot-electron regime.