Fabrication of Nb/Al-N/sub x//NbTiN junctions for SIS mixer applications

Bumble, B.; Leduc, H. G.; Stern, J. A.; Megerian, K. G.

doi:10.1109/77.919288

Cited by 45 publications

(32 citation statements)

References 10 publications

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“…Thus, if a NbTiN / SiO 2 / NbTiN tuning circuit was to be used at frequencies below 0.8 THz, it would be desirable to reduce this heating effect. For example, the use of a Nb/ Al-AlN x / NbTiN junction 20 would allow heat to escape into the top NbTiN wiring layer via the NbTiN junction electrode. ͑Note that the first photon step below the gap voltage is the region in which the mixer's optimum bias voltage is found.͒…”

Section: Discussionmentioning

confidence: 99%

Niobium titanium nitride-based superconductor-insulator-superconductor mixers for low-noise terahertz receivers

Jackson

Lange

Zijlstra

et al. 2005

Journal of Applied Physics

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Integrating NbTiN-based microstrip tuning circuits with traditional Nb superconductorinsulator-superconductor ͑SIS͒ junctions enables the low-noise operation regime of SIS mixers to be extended from below 0.7 to 1.15 THz. In particular, mixers incorporating a NbTiN / SiO 2 / NbTiN microstrip tuning circuit offer low-noise performance below 0.8-0.85 THz, although their sensitivities drop significantly at higher frequencies. Furthermore, a microstrip geometry in which NbTiN is used as the ground plane material only ͑NbTiN / SiO 2 /Al͒ yields significant improvements in the sensitivities of SIS mixers operating up to 1.15 THz, with an upper operating frequency that depends upon the quality of the NbTiN layer, and thus its deposition process. Films deposited at room temperature have T c = 14.4 K and n,20 K ϳ 60 ⍀ cm, and offer low-noise performance up to 1 THz, whereas films deposited at 400°C have T c = 16 K and n,20 K ϳ 110 ⍀ cm, and offer low-noise performance up to 1.15 THz. Taken together, these results demonstrate that the high-frequency surface resistance of a NbTiN layer depends upon the film's structural properties. Most significantly, the drop in performance that is seen at F Ͼ 1 THz in mixers incorporating NbTiN ground planes deposited at room temperature is attributed to nonhomogeneities in the structural and electrical properties of these films, as is the poor performance of mixers that incorporate NbTiN wiring layers at F Ͼ 0.85 THz. The development of these NbTiN-based microstrip tuning circuits will enable the production of low-noise SIS mixers for the 0.8-0.96-and 0.96-1.12-THz frequency bands of the Heterodyne Instrument for the Far Infrared on board the European Space Agency's Herschel Space Observatory.

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Section: Discussionmentioning

confidence: 99%

Niobium titanium nitride-based superconductor-insulator-superconductor mixers for low-noise terahertz receivers

Jackson

Lange

Zijlstra

et al. 2005

Journal of Applied Physics

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“…A route towards higher critical current densities, achieved by replacing with AlN, was first identified by Shiota et al [12] and subsequently explored by others [13], [14]. We have recently developed a technological route to AlN devices suitable for SIS mixers [15] using an ICP approach, which was also proposed in [16] and identified that in comparison to the AlN tunnel barriers have much more uniform tunneling properties.…”

Section: Bandwidth Of Sis Mixersmentioning

confidence: 99%

Bandwidth Limitations of Nb/AlN/Nb SIS Mixers Around 700 GHz

Lodewijk

Zijlstra

Zhu

et al. 2009

IEEE Trans. Appl. Supercond.

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Abstract-We study, using niobium-technology, the bandwidth of SIS mixers operating at frequencies close to the energy-gap frequency. Microstriplines of niobium-silicon dioxide-niobium have different properties for the top and bottom superconductor, which we find to depend on the used fabrication process. Replacing the AlO x tunnel barrier by AlN, the bandwidth increases by 53%. The measurements, using a Fourier Transform Spectrometer (FTS) and performed in ambient air, demonstrate that the bandwidth is no longer limited by the tuning circuit but by the atmospheric absorption of radiation. Excellent noise temperatures are found over a full band of 600 to 720 GHz.

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“…When a normal metal or NbTiN are used in the ground plane of the mixer circuit, a Nb base electrode of the junction must be deposited on the top of the ground plane film. Some intermediate layers may be needed to have a good interface 3 . The etching through the additional layers in the junction structure makes the production process more difficult, and reduces the yield.…”

Section: Approachmentioning

confidence: 99%

“…This motivates research on alternative materials to provide the low loss THz circuits as well as new types of SIS junctions with higher gap voltages. Recent progress in thin film NbTiN technology 3 has given the possibility to create low loss circuits above 0.6-0.7 THz and to improve the performance of the SIS mixers with Nb/AlOx/Nb junctions up to 1 THz 4,5 . Another approach, using a low loss normal metal circuit to build a low noise 1.05 THz SIS mixer, has been demonstrated in 6,7 .…”

Section: Introductionmentioning

confidence: 99%

Low-noise SIS mixer for far-infrared radio astronomy

Karpov

Miller

Rice

et al. 2004

Millimeter and Submillimeter Detectors for Astronomy II

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We present a low noise SIS mixer developed for the 1.2 THz band of the heterodyne spectrometer of the Herschel Space Observatory. The device of this design will be among the first SIS mixers flown in space at Herschel. The developed SIS mixer has a quasi-optical design, with a double slot planar antenna and an extended spherical lens made of pure Si. The SIS junctions are Nb/AlN/NbTiN with the critical current density of about 30 KA/cm2 and with the junction area of a quarter of a micron square. For the ease of the Josephson current suppression, the SIS junctions are diamond-like shaped. The simultaneous suppression of the Josephson currents in the two SIS junctions is a particular advantage of the used shape. A low loss Nb/Au micro-strip transmission line is used for the first time in the mixer circuit well above the gap frequency of Nb.Using the new mixer we demonstrated the minimum uncorrected Double Sideband receiver noise of 550 K (Y=1.34). The minimum receiver noise corrected for the local oscillator beam splitter and for the cryostat window is 330 K, about 6 hν/k, apparently for the first time in the THz frequencies range.

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Fabrication of Nb/Al-N/sub x//NbTiN junctions for SIS mixer applications

Cited by 45 publications

References 10 publications

Niobium titanium nitride-based superconductor-insulator-superconductor mixers for low-noise terahertz receivers

Niobium titanium nitride-based superconductor-insulator-superconductor mixers for low-noise terahertz receivers

Bandwidth Limitations of Nb/AlN/Nb SIS Mixers Around 700 GHz

Low-noise SIS mixer for far-infrared radio astronomy

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