Elementary excitations such as photons, electrons, and spins are investigated and controlled by surface acoustic waves. Photons, electrons, and spins can be manipulated at gigahertz frequencies opening new perspectives for applications in optoelectronic devices.
The optical properties of III-V nanowires and heterostructures are investigated by spatially and time-resolved photoluminescence spectroscopy as well as by cathodoluminescence spectroscopy in a scanning electron microscope. Light-emitting diodes using ensembles of free-standing (In,Ga)N/GaN nanowires are studied using electron beam induced current analysis in a scanning electron microscope and spatially resolved electroluminescence spectroscopy.
Quantum-cascade lasers for the terahertz spectral region are designed, their optical and transport properties are simulated, and complete lasers are realized and their lasing properties are investigated. The lasers usually emit several modes, but can also be realized as distributed-feedback lasers with single-mode operation.
The injection of spins from a ferromagnet into a semiconductor is studied using ferromagnet-semiconductor hybrid structures by looking at their magneto-optical and magneto-transport properties. In order to achieve spin control, all-electrical spin injection and detection are investigated using lateral ferromagnet-semiconductor hybrid devices.
Magneto-transport properties of two-dimensional electron gases on a cylindrical surface are investigated in high magnetic fields and at low temperatures in order to understand the transport of two-dimensional electrons in non-planar geometries.
Electronic transport properties of topological insulators, in which carriers are only transported on the surface and not in the bulk, are examined by studying the weak antilocalization effect due to spin-orbit coupling and the electron-electron interaction.