New materials for quantum Hall resistance standards

Focus: 
Quantum Metrology

Electrical properties of materials are one of the most fundamental information for characterisation. Basic electrical characteristics in terms of type, concentration and mobility of carriers can be obtained from Hall effect measurements of thin layers in applied current and magnetic fields. Quantum Hall (QH) systems are discussed as promising THz detectors. Photoconduction measurements of the HgTe/HgCdTe (MCT) quantum well in Hall bar, Corbino as well as combined Corbino-Hall bar geometry in the quantum Hall (QH) regime are accomplished. FIR photoconduction measurements of the MCT samples are done to contribute to the basic research in photoconduction at QH systems and, in addition, to the development of a sensitive as well as spectra adjustable QH detectors. The materiel system MCT is of interest due to the small effective mass (compared with GaAs) and the smaller magnetic fields for operation. A superconducting 10 T-magnet and an adjustable p-Ge cyclotron resonance laser (the laser as FIR source, wavelength range between 120 -180μ m) are used for the measurements.

Mentor/s: 
Nachtwei
Institution: 
TU Braunschweig
Status: 
completed
Ph.D. student: 
Bugár