Nano Ma­ter­i­als

Group Mem­bers

Group Leaders Vitalii Sichkovskyi, Johann Peter Reithmaier
PhD Students Sven Bauer, Tanja Finke, Balasubramanian Ramasubramanian
Technicians
Master Students
 Dirk Albert
 Cedric Corley

Ob­ject­ives

One- and zero-dimensional semiconductor structures attract significant research interest due to their unique electronic and optical properties, based on quantum confinement of the electron and hole motion. One of the major goals of our group is the development and optimization of zero-dimensional structures, known as quantum dots (QDs), which should contribute to the development of new optoelectronic devices with significantly improved performance.

The mostly used method for the growth of quantum dot structures is based on self-assembled Stranski-Krastanov growth mode by molecular beam epitaxy (MBE), which can be combined with pre-patterning of the substrate by electron beam lithography, allowing control of the density and dimensions of the structures.

Our current research activities are focused on the investigation of the influence of the MBE process parameters on the formation and growth of quantum dot structures, based on GaAs, InP, and Si substrates by Varian Gen II MBE system. The density and morphology of the QDs are assessed using atomic force microscopy. Their optical properties are characterized ex-situ by low-temperature photoluminescence (PL) spectroscopy.

Pro­jects

Lit­er­at­ure

Publications

Overview talks

Pic­ture gal­lery

Varian Gen II MBE system.
Varian Gen II MBE system.
Photoluminescence spectrum of the InAs QD layer embedded in InAlGaAs measured at 10 K. The inset shows a 1x1 μm2 AFM scan of an uncapped self-organized InAs QDs structure.
Photoluminescence spectrum of the InAs QD layer embedded in InAlGaAs measured at 10 K. The inset shows a 1x1 μm2 AFM scan of an uncapped self-organized InAs QDs structure.
Light output vs drive current of 2.4 mm long cavity and 2 μm wide as cleaved ridge waveguide laser with single QD layer in the active region measured at 11°C. The inset shows the emission spectrum.
Light output vs drive current of 2.4 mm long cavity and 2 μm wide as cleaved ridge waveguide laser with single QD layer in the active region measured at 11°C. The inset shows the emission spectrum.
5 x 5 µm2 AFM image of high density InAs/GaAs core-shell QDs directly grown on 5°-off (001) Si substrate.
5 x 5 µm2 AFM image of high density InAs/GaAs core-shell QDs directly grown on 5°-off (001) Si substrate.
Cross-sectional high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) micrograph of the InAs/InAlGaAs/InP QDs structure viewed in the [110] direction (perpendicular to the QDs elongation direction).
Cross-sectional high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) micrograph of the InAs/InAlGaAs/InP QDs structure viewed in the [110] direction (perpendicular to the QDs elongation direction).
Results of atom probe tomography on InAs/InAlGaAs/InP QDs structure: (a) plane view of In atoms distribution for isosurface corresponding to 75% of In content); (b) concentration of particular atoms across the height of a dot.
Results of atom probe tomography on InAs/InAlGaAs/InP QDs structure: (a) plane view of In atoms distribution for isosurface corresponding to 75% of In content); (b) concentration of particular atoms across the height of a dot.
MBE team (July 2016). From the left: Dirk Albert, Sven Bauer, Marc S. Wolf, Vitalii Sichkovskyi, Saddam Banyoudeh.
MBE team (July 2016). From the left: Dirk Albert, Sven Bauer, Marc S. Wolf, Vitalii Sichkovskyi, Saddam Banyoudeh.