Niobium Hot Electron Bolometer Development for a Submillimeter Heterodyne Array Camera

We are developing a proof-of-concept for a diffusion cooled hot electron bolometer (HEB) array submillimeter camera. The ultimate objective is to create a working 64 pixel array with the University of Arizona for use on the Heinrich Hertz Telescope. We have fabricated Nb HEBs using a novel angle deposition process. We have characterized these devices using heterodyne mixing at 20 GHz. We also report on optimizations in the fabrication process that improve device performance and a dc screening test for device quality. Using this process, HEBs with a sharp resistive transition (<300 mK) can consistently be produced. These devices have good suppression of superconductivity in the contact pads, with a pad transition ~1 K below the main bridge transition. Furthermore, the bandwidth was investigated above and below the pad transition and found to be ~15% larger for 400 nm long bridges with non- superconducting contact pads.