Nanophysics

Research activities

The research of our nanostructure group focuses on the fabrication, characterization and theoretical modelling of quantum wires and quantum dots. In addition photonic devices based on such structures are investigated. Emphasis is put on self-organized or self-assembled structures, for which the interfaces of the active regions are formed in-situ during epitaxy and which require no or only minimal artificial patterning. This includes quantum wires grown in V-grooves and quantum dots fabricated using Stranski-Krastanow growth (in the coherent island regime). Growth techniques are MOCVD and also MBE (in collaboration) in the strained material system InGaAs/GaAs, GaSb/GaAs and other III-V compound heterostructures. Recent highlights were the demonstration of quantum dot lasers and the detection of ultrasharp single quantum dot recombination lines. Actual research topics are:

• Growth of self-organized nanostructures.
• Correlation of growth conditions and nanostructure morphology, understanding of the underlying formation processes and driving forces.
• Mechanisms of selfordering in quantum dot arrays.
• X-ray diffraction from ultrasmall nanostructures.
• Correlation of morphology and optical properties, spectrally and spatially resolved, single dot experiments.
• Carrier dynamics, capture, cooling, recombination, especially electron-phonon interaction in low- dimensional systems.
• New theoretical approachs to carrier statistics in quantum dots.
• Processing and characterization of quantum wire and dot lasers.
• Simulation of strain relaxation and electronic levels in arbitrarily shaped nanostructures.
• Staggered band line-up heterointerfaces on planar and corrugated substrates.

Experimental Facilities

The research area has an AIXTRON MOCVD machine, semiconductor processing, photo- and holographic lithography and is equipped with a variety of characterization methods including X-ray diffraction, cw and time-resolved photoluminescence and PL excitation, spatially, spectrally and time-resolved cathodoluminescence, calorimetric absorption spectroscopy, DLTS and streak cameras. Additonally high frequency electrical measurement techniques up to 50GHz are available.

Some links for nano stuff...

• Nanotechnology
• Sonderforschungsbereich 296

Last update: Jul-24-1995.

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