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Research Activities in the group "Semiconductor Physics"
Internet:
www.physnet.uni-hamburg.de/iap/group_h/en/info/index.html The
research of the "Semiconductor" Group at the Institute of
Applied Physics and Microstructure Advanced Study Institute, Hamburg,
MARCH, focuses on the preparation of nanostructured semiconductor,
metal, and ferromagnetic systems, and the investigation of the
electronic, spintronic and photonic properties of these systems.
In
close cooperation with the group of Professor Hansen we can prepare
tailored GaAs- or InAs-GaAlAs-Heterostructures or self organized
InAs-Quantumdots by MBE (Molecular Beam Epitaxy). In our
professional cleanroom we can fabricate lateral nanostructures using
ebeam and holographic lithography, plasma etching and deposition and
various evaporation and sputtering techniques.
The
experimental research is performed in three groups headed by
enthusiastic young postdocs.
Dr. Christian Schüller and his group investigate quantum systems
with optical techniques. Utilizing the different selection rules,
Raman spectroscopy gives access to charge density, spin density and
single particle excitations in quantum well, wires and dots. With
photoluminescence we investigate charged excitons in the fractional
quantum Hall regime, self assembled InAs-quantum dots charged with
well defined numbers of electrons in gated arrangements and,
utilizing imaging CCD arrays, single quantum dots prepared by wet
chemistry or lateral patterning of quantumwell systems. Christian
Schüller also studies ultrafast processes with femtosecond
spectroscopy in modulation-doped heterostructures. We also prepare
and investigate photonic band gap systems, microcavities and micro
discs with whispering gallery modes.
Dr. Dirk Grundler's and his group's interest are the magnetism of low
dimensional electron systems or nanostructured ferromagnets and the
spintronics. Utilizing sophisticated SQUID arrangements we were able
to measure the magnetization of the fractional quantum Hall state. We
have also developed monolithic cantilever with integrated
quantumwells, wires and dots. Small magnetic forces acting on the
cantilever can be detected using a sensitive capacitance bridge and
allow us to measure magnetization as small as 10exp-13 J/T.
Measurements on 2DES in modulation doped quantum wells show
beautifully de Haas van Alphen oscillations and, at low temperatures,
quasi persistent (t >1h) edge currents. Ferromagnetic nanodots
have been integrated on micro Hall bars and the local and non local
response has been measured. In recent experiments we have
investigated the extraordinary magnetoresistance effect by in situ
cleaved edge overgrowth samples. Dirk Grundler has also strong
activities in spintronics, in particular the Rashba effect and the
optimization of the spin injection from ferromagnets to 2DES
utilizing band structure effects.
More details of our research are found at |