19 July 2016 Low-volume aluminum and aluminum / titanium nitride bilayer lumped-element kinetic inductance detectors for far-infrared astronomy
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We present the design and characterization of low-volume, lumped-element aluminum kinetic inductance de- tectors for sensitive far-infrared astronomy observations. The lumped-element kinetic inductance detectors are comprised of meandered inductors that serve as radiation absorbers in parallel with interdigitated capacitors, forming high quality factor resonators. Low inductor volumes lead to low noise equivalent powers by raising quasiparticles densities, and hence responsivities, with respect to larger volumes. Low volumes are achieved with thin (20 nm), narrow (150 nm) inductors. The interdigitated capacitor architecture is designed to mitigate two-level system noise by lowering electric fields in the silicon substrate. Resonance frequencies are in the range of 190 to 500 MHz, with measured internal quality factors in excess of 1 x 105. In a prior incarnation, a titanium nitride layer on top of the aluminum served as a protective layer, but complicated the superconducting proper- ties. These results were reported previously. In the current incarnation, the aluminum layer is left bare with no titanium nitride over-layer. The results for these bare aluminum devices include a yield of 88%, frequency responsivity of 109 W-1, and noise equivalent power of 1 x 10-17 W Hz-1/2 for a 350μm array. There is no evidence for 1=f noise down to at least 200 mHz. The sensitivity is currently limited by white noise, very likely from stray light in the testbed; for this detector design, sensitivities limited by generation-recombination noise in a lower-background environment should be several orders of magnitude lower.
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Jason Glenn, Jason Glenn, Adalyn Fyhrie, Adalyn Fyhrie, Jordan Wheeler, Jordan Wheeler, Peter K. Day, Peter K. Day, Byeong Ho Eom, Byeong Ho Eom, Henry G. Leduc, Henry G. Leduc, } "Low-volume aluminum and aluminum / titanium nitride bilayer lumped-element kinetic inductance detectors for far-infrared astronomy", Proc. SPIE 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, 99140Z (19 July 2016); doi: 10.1117/12.2233649; https://doi.org/10.1117/12.2233649

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