Optimization of hot-electron bolometers for THz radiation

Hot-electron bolometers are fast and low noise radiation detectors which can be used for many different applications. Especially in astrophysics there is strong need for low-noise detectors with a large bandwidth of several gigahertz. Hotelectron bolometers fabricated from ultra-thin superconducting films can satisfy these requirements. In such detectors the electron and the phonon subsystem can thermally decouple at low temperatures. Making use of this hot-electron effect low noise detectors with a large bandwidth and a high sensitivity can be realized. The aim of this work was to optimize the fabrication process of hot-electron bolometers and gain a deeper understanding of the underlying processes. These results were used to realize detectors with a much lower noise and a very large bandwidth. To achieve this, the fabrication of the superconducting thin films was optimized and the superconducting properties of the films were analyzed. In a further step the thermal coupling between the superconducting thin-film and the used silicon substrate was studied and a new method for thermal decoupling of the thin film was developed. Detectors fabricated using the results obtained from these optimization showed a record value for the noise temperature.