Investigation of Novel Superconducting Hot Electron Bolometer Geometries Fabricated With Ultraviolet Lithography

While the superconducting community has developed various techniques for the fabrication of nanoscale hot electron bolometers (HEB), the basic structure of an HEB microbridge has been fairly consistent. A typical HEB used in a cryogenic terahertz mixer consists of a thin strip of superconductor contacted on opposite ends by small metal contact pads in a planar configuration. Both the physics and typical fabrication requirements for HEBs inspire this traditional construction. In this paper, however, we demonstrate that alternative HEB geometries are possible, which can in some cases improve the ease of fabrication, alter device characteristics, or alleviate certain device limitations. New HEB structures and associated fabrication processes are presented, building on previous work using the SSNaPS method of nanoscale patterning. These include very short niobium nitride HEBs with self-aligned bridge etch masks, and sidewall-patterned niobium HEB microbridges.