Investigation of YBCO bolometers for THz wave detection

Abstract

The work presented in this master thesis is about the fabrication and char- acterization of bolometers based on thin films of YBa2Cu3O7−δ dedicated for detection of radiation in the THz-regime. A cleanroom process was developed to fabricate antenna-integrated bolometers on Al2O3 substrates. This process is described in detail to enable reproduction of the results. The same devices were tested at room temperature and 77 K as both direct and heterodyne detec- tors for a broad frequency range, 100 GHz to 1.63 THz. As direct detectors, the bolometers combine a responsivity of 450 V/W and a noise level of 20 pW/Hz1/2 at 77 K. At room temperature the corresponding numbers were 15 V/W and 450 W/Hz1/2, making the bolometers competitive to established room temper- ature detector technologies. These properties were combined with a relatively fast response time of 300 ps and 2 ns at 77 K and room temperature, respec- tively. As heterodyne detectors, the bolometers exhibited a conversion gain of -24 dB and -28 dB at 77 K and room temperature, respectively. As the title of the thesis indicates, focus has been on investigation rather than optimization of the devices. Hence, there is still much to be done to obtain the best possible performance.