We report on the development of the first integrated mid-infrared, far-infrared and terahertz optical Hall effect instrument, covering an ultra wide spectral range from 3 cm\(^{-1}\) to 7000 ...cm\(^{-1}\) (0.1-210 THz or 0.4-870 meV). The instrument comprises four sub-systems, where the magneto-cryostat-transfer sub-system enables the usage of the magneto-cryostat sub-system with the mid-infrared ellipsometer sub-system, and the far-infrared/terahertz ellipsometer sub-system. Both ellipsometer sub-systems can be used as variable angle-of-incidence spectroscopic ellipsometers in reflection or transmission mode, and are equipped with multiple light sources and detectors. The ellipsometer sub-systems are operated in polarizer-sample-rotating-analyzer configuration granting access to the upper left \(3\times 3\) block of the normalized \(4\times 4\) Mueller matrix. The closed cycle magneto-cryostat sub-system provides sample temperatures between room temperature and 1.4 K and magnetic fields up to 8 T, enabling the detection of transverse and longitudinal magnetic field-induced birefringence. We discuss theoretical background and practical realization of the integrated mid-infrared, far-infrared and terahertz optical Hall effect instrument, as well as acquisition of optical Hall effect data and the corresponding model analysis procedures. Exemplarily, epitaxial graphene grown on 6H-SiC, a tellurium doped bulk GaAs sample and an AlGaN/GaN high electron mobility transistor structure are investigated. The selected experimental datasets display the full spectral, magnetic field and temperature range of the instrument and demonstrate data analysis strategies. Effects from free charge carriers in two dimensional confinement and in a volume material, as well as quantum mechanical effects (inter-Landau-level transitions) are observed and discussed exemplarily.
A new multi-wavelength in situ ellipsometer capable of acquiring accurate ellipse-metric data at 44 wavelengths from 415 to 750 nm in less than 1 s has been directly mounted on a molecular beam ...epitaxy (MBE) growth system. In contrast to single-wavelength ellipsometers, enough measured data is available to allow calculation of layer thickness, composition, temperature and exact angle of incidence. In situ monitoring and real-time analysis was used to control the growth process of GaAs/AlGaAs Bragg reflectors with a center wavelength of 1000 nm. The layer thickness is controlled very accurately even though ellipsometric data was acquired only every 3 s. The accuracy of shutter timing can be controlled very precisely, even allowing for slow ellipsometric acquisition rates and substrate wobble due to MBE substrate rotation.
The control algorithm for the two reflectors did not attempt to control the Al composition of an individual AlGaAs layer, but the measured composition was used to adjust the Al cell temperature for the next AlGaAs layer. For purposes of comparison, the FastDyn fitting routine was used with another reflector to simultaneously control the thickness and surface composition of the AlGaAs layers. An overview of the hardware and software integration on the MBE system will be given. The in situ measurements during the growth control were later compared with ex situ measurements made with the spectroscopic ellipsometer system variable angle spectroscopic ellipsometry (VASE).
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