Elementary excitations controlled by acoustic fields are investigated in solids by optical spectroscopy. Photons, electrons, and spins can be manipulated at gigahertz frequencies using surface acoustic waves 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. Of particular importance is the correlation between structural defects and optical properties in III-V nanowires.
Quantum-cascade lasers for the terahertz spectral region are designed, their optical as well as transport properties are simulated, complete lasers are realized, and their lasing properties are investigated. These lasers are compact sources, can be operated in single mode, exhibit typical optical output powers between several mW and several tens of mW, and function at temperatures, which do not require cooling with liquid helium.
The generation and the transport of spins in ferromagnet-semiconductor hybrid structures are studied by analyzing their magneto-optical and magneto-transport properties. In order to achieve spin control, all-electrical spin injection and detection are investigated using lateral and vertical spin valve devices.
The electronic and spin properties of semiconductor-based nanoscale systems such as nanowires and quantum dots defined laterally in heterostructures are studied by quantum transport experiments aiming at the development of new strategies for information processing.
The electronic transport properties of topological insulators, in which charges are only transported on the surface and not in the bulk, are investigated by examining the weak antilocalization effect due to spin orbit coupling and the electron-electron interaction.