Semiconductor Spectroscopy

The facilities for optical spectroscopy include Raman spectroscopy to study the vibrational modes in semiconductor films, heterostructures, and nanowires as well as in topological insulators and graphene. Continuous-wave photoluminescence and photoluminescence excitation spectroscopy from the ultraviolet (244 nm) to the near-infrared spectral region (1.7 μm) are used to investigate III-V films, heterostructures, and nanowires. The spectroscopic techniques for the near-infrared to ultraviolet spectral regions such as Raman and photoluminescence spectroscopy can also be used with a spatial resolution down to about 0.5 μm and in magnetic fields up to 8 T.

With cathodoluminescence spectroscopy and imaging in a scanning electron microscope, the spatial resolution can be enhanced into the range of ten nanometers. In addition, element identification is achieved by energy- and wavelength-dispersive x-ray spectroscopy, and the crystallographic orientation as well as the strain state can be determined using electron backscatter diffraction.

Time-resolved photoluminescence spectroscopy on a pico- to microsecond time scale from the ultraviolet (240 nm) to the near-infrared spectral region (1.3 μm) and pump-and-probe spectroscopy with a subpicosecond time resolution are employed to investigate the carrier and polarization dynamics in III-V films, heterostructures, and nanowires.

Fourier-transform spectroscopy is used in the far-infrared or terahertz spectral region to record the lasing parameters of quantum-cascade lasers and in the mid-infrared region to study vibrational modes.

The magneto-transport experiments on ferromagnet-semiconductor hybrid devices, semiconductor-based nanoscale systems, and topological insulators can be performed in magnetic fields up to 16 T and at temperatures down to 20 mK.