Abstract
As the demand for faster electronics increases, eventually making the transition from GHz operating frequencies to those in the THz regime, it has become crucial to investigate and understand the electronic properties of semiconductors in this frequency range. Due to the limitations of electronic measurement equipment, one cannot straightforwardly probe these electronically. One solution is to probe these properties optically by measuring the magneto-transmission, which contains information about the AC conductivity. Alongside looking into the AC conductivity, the researchers have realized a setup with which we can resistively detect cyclotron resonances. The benefit of a resistive detection method is that one can access the THz electronic properties and electronic excitations in nano-devices, which is not possible with direct transmission experiments.
Using the HFML-FELIX installation, this thesis investigated the AC conductivity of III-V semiconductors for frequencies well beyond the typical electron scattering rates. The THz conductivity was determined by fitting the magneto-transmission spectra with a conductivity model based on the Lifshitz-Kosevich formalism. The measured difference in the sample resistance with and without the FEL macropulse on the sample resulted in the detection of a resistive and thermoelectric signal, both containing signatures of a cyclotron resonance with the expected dependence on field and frequency.
