Optimization of Parameters of MgB 2 Hot-Electron Bolometers

Hot-electron bolometers (HEBs) made with MgB 2 have proven to have a large intermediate frequency and have shown potential for a low noise into the terahertz range. Although practical results from these mixers have been achieved fairly quickly, effort is still needed to realize an MgB 2 HEB with improved sensitivity to compete with state-of-the-art mixers. Here, we present the results of our mixer work to achieve MgB 2 HEBs based on hybrid physical chemical vapor deposition grown films, with improved sensitivity and higher temperature operation. A new fabrication process is developed which utilizes even thinner films (<;10 nm) allowing for the improvement of the impedance match of the mixer device with the Au spiral antenna. Integrated superconducting contacts prevent deterioration of the sensitivity due to the electron diffusion. The mixer noise temperature is 2000 and 3600 K at 600 and 1.9 THz, respectively, with minimal dependence on the bath temperature until over 20 K. The noise bandwidth of the mixer is 6.5 GHz at 4.2 K and is expected to be larger at higher operating temperature.