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

Lodewijk, C. F. J.; Zijlstra, T.; Zhu, Shaojiang; Mena, F. P.; Baryshev, A.; Klapwijk, T. M.

doi:10.1109/tasc.2009.2018231

Cited by 8 publications

(4 citation statements)

References 16 publications

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“…In the case of junctions with AlN barrier there are still uncertainties concerning the specific capacitance of junctions as function of current density. In [11], it is assumed to be 60 fF/ m for a critical current density of 56 kA/cm . On the other hand, it was measured as 85 fF/cm for 50 kA/cm in [12] and, estimated as 100 fF/cm for 20 kA/cm in [13] and [14].…”

Section: A Fts Resultsmentioning

confidence: 99%

High-Gap Nb-AlN-NbN SIS Junctions for Frequency Band 790–950 GHz

Khudchenko

Baryshev

Rudakov

et al. 2016

IEEE Trans. THz Sci. Technol.

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We have designed, fabricated, and tested superconductor-insulator-superconductor (SIS) mixers based on Nb/AlN/NbN twin tunnel junctions for waveguide receivers operating in a frequency range of 790-950 GHz. Electromagnetic simulations and measurement results of the mixer performance are presented. The junctions have a high gap voltage of 3.15 mV and a high current density of about 30 kA/cm , providing a wide receiver band, which was confirmed by Fourier transform spectrometer (FTS) and noise temperature measurements. The corrected receiver noise temperature varies from 240 K at low frequencies to 550 K at the high end of the band. The influence of the SIS junction heating on its characteristics has been studied and compared to another similar high current density technologies. The heating does not have a critical impact on the mixer performance.

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Section: A Fts Resultsmentioning

confidence: 99%

High-Gap Nb-AlN-NbN SIS Junctions for Frequency Band 790–950 GHz

Khudchenko

Baryshev

Rudakov

et al. 2016

IEEE Trans. THz Sci. Technol.

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“…For correct calculation, we should exactly know the specific capacitance of the junctions with a tunnel layer of aluminum nitride (AlN). According to [3], a specific capacitance of 60 fF/µm 2 is reached for a critical current density of 56 kA/cm 2 , whereas in [4], a specific capacity of 85 fF/µm 2 for a critical current density of 50 kA/cm 2 is mentioned. To reduce the uncertainty and definitely realize the required input band, the samples calculated for various specific capacitances were included to the manufactured series.…”

Section: Variations In the Receiving-structure Characteristicsmentioning

confidence: 99%

The 700–950 GHz Superconducting Receiving Structures for Radio Astronomy

Rudakov

Koshelets

Baryshev

et al. 2017

Radiophys Quantum El

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We have designed, fabricated, and tested the waveguide receiving element, which is based on the tunnel superconductor-insulator-superconductor structures, for the frequency range 790-950 GHz. Two Nb/AlN/NbN tunnel junctions are incorporated in a microstrip line consisting of the bottom NbTiN-film electrode with a thickness of about 300 nm and the top 500 nm-thick aluminum electrode. The production-process optimization allows one to ensure the following characteristics of these junctions: submicron area (0.5 µm 2 for each junction), current density about 30 kA/cm 2 , and band gap width 3.2 mV. Such tunnel junctions ensure the receiver operation in a wide frequency range (700-950 GHz), which was confirmed by the Fourier transform spectroscopy and the noise-temperature measurements. At a frequency of 725 Hz, the corrected noise temperature of the receiver amounts to 120 K, which is only threefold greater than the quantum limit hf /k B , where h is the Planck's constant, f is the frequency, and k B is Boltzmann's constant. In the upper part of this frequency range, the noise temperature increases up to 390 K.

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“…uperconductor-Insulator-Superconductor (SIS) mixers have become the cornerstone of most low noise heterodyne receivers for radio astronomical spectroscopy in millimeter and submillimeter range [5]. In the last few years there has been a growing interest in improving capabilities of radio astronomical receivers in terms of wider instantaneous RF and IF bandwidth [6]- [8]. One of the advantages of a wide RF instantaneous bandwidth is to reduce the number of instruments for conducting observations.…”

Section: Introductionmentioning

confidence: 99%

Specific Capacitance Dependence on the Specific Resistance in Nb/Al–AlOx/Nb Tunnel Junctions

Aghdam

Rashid

Pavolotsky

et al. 2017

IEEE Trans. THz Sci. Technol.

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The junction specific capacitance (Cs) is an essential parameter in designing tuning circuitry for Superconductor-Insulator-Superconductor (SIS) mixers. However, our knowledge of the junction capacitance only relies on the few available empirically obtained Cs vs. specific normal resistance (RnA) relations, which are inconsistent especially at low RnA values, RnA < 40 Ω.µm 2. In this paper, we report the Nb/Al-AlOx/Nb SIS junction capacitance data from our recently presented direct microwave (4 GHz) measurements at 4K for junctions with various RnA values ranging from 8.8 to 68 Ω.µm 2. New insight is provided into the extraction of the true geometrical specific capacitance of SIS junctions. We show that, even at such low microwave frequencies, the so-far-neglected nonlinear susceptance is significant, especially for junctions with low RnA values. This susceptance originates from the real part of the response function, IKK, which can be calculated through the Kramers-Kronig transform of the DC tunnel current. The new specific capacitance, which accounts for this contribution is presented as a function of RnA. We provide an improved and more accurate Cs (RnA) relation, which can be a reliable and useful tool for circuit designers. The obtained Cs (RnA) relation is compared with those available in the literature, and the possible reasons giving rise to the disparity among these relations are discussed. By comparing the modelled and the measured noise temperature of the APEX SHeFI band 3 (385-500 GHz) DSB mixer, we show that the new Cs (RnA) relation offers a great potential for improving the performance of SIS mixers.

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

Cited by 8 publications

References 16 publications

High-Gap Nb-AlN-NbN SIS Junctions for Frequency Band 790–950 GHz

High-Gap Nb-AlN-NbN SIS Junctions for Frequency Band 790–950 GHz

The 700–950 GHz Superconducting Receiving Structures for Radio Astronomy

Specific Capacitance Dependence on the Specific Resistance in Nb/Al–AlOx/Nb Tunnel Junctions

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