Tantalum STJ for photon counting detectors

• Published in: IEEE transactions on applied superconductivity Vol. 15; no. 2; pp. 587 - 590
• Main Authors: Jorel, C., Feautrier, P., Villegier, J.-C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-06-2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum; Applied sciences; Astronomy; Capacitors. Resistors. Filters; Circuit properties; Condensed Matter; Counting; Counting circuits; Detectors; Electric, optical and optoelectronic circuits; Electrical engineering. Electrical power engineering; Electrodes; Electronic circuits; Electronics; Energy resolution; epitaxial layers; Exact sciences and technology; Fabrication; Frequency filters; Infrared detectors; Josephson junctions; Materials Science; near infrared; Optoelectronic devices; photon counting; Photons; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; STJ; Superconducting epitaxial layers; Superconducting photodetectors; Superconductivity; Tantalum; Various equipment and components; Wavelengths; X-ray detection; X-ray detectors; Digital filtering; Resolving power; near infrared; Absorbent material; Photon counting; Measurement sensor; STJ; epitaxial layers; Experimental study; Quantum yield; Photodetector; Thin film; Near infrared radiation; Digital filter; Manufacturing process; Superconducting tunnel junction; Optoelectronic device; tantalum; Astronomy; Superconducting tunnel junctions; astronomy; photon counting
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2005.849949

Superconducting Tunnel Junctions (STJ's) are currently being developed as photon detectors for a wide range of applications. These detectors are used because they are energy resolving photon counters, and they can be used from the infrared (2 /spl mu/m) to X-ray wavelengths with good quantum efficiency (80%). At visible wavelengths, the spectral resolution of STJ's can exceed one part in ten. The goal of this work is to develop STJ's for use in low-light astronomical applications in the near infrared. This work emphasizes two points: improvement of the epitaxial tantalum absorber and the development of a new fabrication process for Ta/Al-AlOx-Al/Ta STJ's. The main features of this process are that pixels have aligned electrodes and vias patterned through a protecting SiO/sub 2/ layer. These vias are used to contact the top electrode layer of the STJ. The AlOx tunnel barrier has symmetric Al-Ta trap layers on either side. The 150 nm thick Ta absorber is epitaxially grown on top of a thin Nb seed layer. Photon counting experiments with theses devices are presented at /spl lambda/=0.78 /spl mu/m. Digital filtering methods are used to compute the photon counting data in order to minimize noise.