Fabrication of a diffusion cooled superconducting hot electron bolometer for THz mixing applications

Recent interest in bolometers for heterodyne mixing applications has prompted development of microbridges which are small enough to allow electron diffusion to dominate over electron-phonon interaction as a cooling mechanism. Prior results at 533 GHz have demonstrated several GHz intermediate frequency (IF) bandwidth. Here we describe our processing method in which the bolometer element is a 10 nm thin film of niobium defined by electron beam lithography down to dimensions of 80 nm. This microbridge is embedded in a normal metal (Au) antenna structure for 1.2 and 2.5 THz applications.