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Superconducting Transition and Heterodyne Performance at 730 GHz of a Diffusion-cooled Nb Hot-electron Bolometer Mixer

J. R. Gao, M. E. Glastra, R. H. Heeres, W. Hulshoff, D. Wilms Floet, Herman van de Stadt, T. M. Klapwijk, Th. de Graauw

Published Jan 1, 1997• 1 citation

Abstract

We report two typical experimental results of waveguide diffusion-cooled Nb hotelectron bolometer (HEB) mixers. The device is a thin (10 nm) Nb bridge with a length of 0.3 Am and a width of 0.9 pm and is defined using photolithography. In the first experiment, the resistance of a HEB is studied as a function of temperature. We observe two critical temperatures, which correspond to the 71. of the Nb bridge and the T, of the Nb under the Au pads, respectively. These two 71. define a superconducting transition width AT of a HEB. The reduced T. of the Nb under the Au pads is explained by the superconducting proximity effect. In the second experiment, we measure relative conversion efficiency vs intermediate frequency (IF) by using two coherent sources, a carcinotron and a Gunn oscillator, and determine an IF roll-off (/F, 011 ,ff ) between 0.6 and 1.2 GHz, in agreement with a value estimated in terms of the diffusion-cooled model.

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