Hot-Electron Bolometer Mixers with in Situ Contacts
We report on the latest achievements in the development of superconducting hot-electron bolometer mixers for terahertz superheterodyne receivers. We consider application ranges of such receivers and requirements for the basic characteristics of the mixers. Main features of the mixers, such as noise temperature, gain bandwidth, noise bandwidth, and required LO power, have been improved significantly over the past few years due to hard work, both in terms of the element fabrication quality and in terms of understanding of the physics of the processes occurring in the hot-electron bolometer mixers. Contacts between the superconducting bridge and the planar antenna play a key role in the mixer operation. Improvement of the contacts leads at the same time to a decrease in the noise temperature and an increase in the gain bandwidth of a mixer.