Dr. Saskia F. Fischer

Ruhr-Universität Bochum Lehrstuhl für Werkstoffe und Nanoelektronik Universitätsstraße 150 Gebäude IC 2 44780 Bochum

Tel: (0234) 32�25760 Fax: (0234) 32�14166 Email: saskia.fischer@ruhr-uni-bochum.de

Prof. Dr. Ulrich Kunze

Ruhr-Universität Bochum Lehrstuhl für Werkstoffe und Nanoelektronik Universitätsstraße 150 Gebäude IC 2 44780 Bochum

Tel: (0234) 32�22300 Fax: (0234) 32�14166 Email: ulrich.kunze@ruhr-uni-bochum.de

Spin-dependant electron transport in GaAs/AlGaAs nanostructures

The aim of this project is to investigate spin-dependent ballistic transport in nanoscale GaAs/AlGaAs field-effect heterostructures. Starting materials are modulation doped heterostructures with two-dimensional electron gases of high mobilities (> 106 cm2/Vs) from which Aharonov-Bohm ring structures are defined by electron-beam lithography and wetchemical etching. Local top and side gates will be used to control the electron densities in the electron wave guides of the ring. Four-terminal measurements of current and voltage characteristics will be taken as a function of top and side gate voltages and magnetic fields at low temperatures (less 4.2 K). Injection of spin polarized electrons in the ring is planned by using a quantum point contact with ultra-large subband separations (>10 meV) as spin filter element in inplane magnetic fields. The amplitude and phase of the Aharonov-Bohm conductance oscillations will be measured for different operating modes of the injecting quantum point contact. Up-to-date, the transport in the mode occupation below the first mode of a quantum point contact is discussed with spin-related mechanisms and remains an unresolved issue. The long-term goal is the investigation of spin-related dephasing mechanisms in the electronic quantum transport by adding a single-electron transistor with tunable coupling to the ring structure.