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Author Larrey, V.; Villegier, J. -C.; Salez, M.; Miletto-Granozio, F.; Karpov, A.
Title (down) Processing and characterization of high Jc NbN superconducting tunnel junctions for THz analog circuits and RSFQ Type Journal Article
Year 1999 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal
Volume 9 Issue 2 Pages 3216-3219
Keywords RSFQ, NbN, SIS
Abstract A generic NbN Superconducting Tunnel Junctions (STJ) technology has been developed using conventional substrates (Si and SOI-SIMOX) for making THz spectrometers including SIS receivers and RSFQ logic gates. NbN/MgO/NbN junctions with area of 1 /spl mu/m/sup 2/, Jc of 10 kA/cm/sup 2/ and low sub-gap leakage current (Vm>25 mV) are currently obtained from room temperature sputtered multilayers followed by a post-annealing at 250/spl deg/C. Using a thin MgO buffer layer deposited underneath the NbN electrodes, ensures lower NbN surface resistance values (Rs=7 /spl mu//spl Omega/) at 10 GHz and 4 K. Epitaxial NbN [100] films on MgO [100] with high gap frequency (1.4 THz) have also been achieved under the same deposition conditions at room temperature. The NbN SIS has shown good I-V photon induced steps when LO pumped at 300 GHz. We have developed an 8 levels Al/NbN multilayer process for making 1.5 THz SIS mixers (including Al antennas) on Si membranes patterned in SOI-SIMOX. Using the planarization techniques developed at the Si-MOS CEA-LETI Facility, we have also demonstrated on the possibility of extending our NbN technology to high level RSFQ circuit integration with 0.5 /spl mu/m/sup 2/ junction area, made on large area substrates (up to 8 inches).
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Call Number Serial 1081
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Author Gol’tsman, G. N.; Gershenzon, E. M.
Title (down) Phonon-cooled hot-electron bolometric mixer: overview of recent results Type Journal Article
Year 1999 Publication Appl. Supercond. Abbreviated Journal Appl. Supercond.
Volume 6 Issue 10-12 Pages 649-655
Keywords NbN HEB mixers
Abstract The paper presents an overview of recent results for NbN phonon-cooled hot electron bolometric (HEB) mixers. The noise temperature of the receivers based on both quasioptical and waveguide versions of HEB mixer has crossed the level of 1 K·GHz−1 at 430 GHz (410 K) and 600–650 GHz (480 K) and is close to this level at 820 GHz (1100 K) and 900 GHz (980 K). The gain bandwidth measured for quasioptical HEB mixer at 620 GHz reached 4 GHz and the noise temperature bandwidth was almost 8 GHz. Local oscillator power requirements are about 1 μW for mixers made by photolithography and are about 100 nW for mixers made by e-beam lithography. The studies in terahertz receivers based on HEB superconducting mixers now present a dynamic, rapidly developing field.
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ISSN 0964-1807 ISBN Medium
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Notes Approved no
Call Number Serial 1564
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Author Ynvesson, K. Sigfrid; Kollberg, Erik L.
Title (down) Optimum receiver noise temperature for NbN HEB mixers according to standard model Type Conference Article
Year 1999 Publication Proc. 10th Int. Symp. Space Terahertz Technol. Abbreviated Journal
Volume Issue Pages 566-582
Keywords HEB mixer model, standard model, electro-thermal feedback, self-heating parameter, heating efficiency
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Call Number Serial 895
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Author Semenov, A. D.; Gol'tsman, G. N.
Title (down) Non-thermal response of a diffusion-cooled hot-electron bolometer Type Journal Article
Year 1999 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 9 Issue 2 Pages 4491-4494
Keywords HEB mixers, non-thermal
Abstract We present an analysis of a diffusion-cooled hot-electron bolometer in the limiting case of a weak thermalization of non-equilibrium quasiparticles. We propose a new model relying on the non-thermal suppression of the superconducting energy gap by excess quasiparticles. Using material parameters typical for Al, we evaluate performance of the bolometer in the heterodyne regime at terahertz frequencies. Estimates show that the mixer may have quantum limited noise temperature and a few tens of GHz bandwidth, while the required local oscillator power is in the /spl mu/W range due to in-effective suppression of the energy gap by quasiparticles with high energies.
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ISSN 1051-8223 ISBN Medium
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Notes Approved no
Call Number Serial 1567
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Author Schubert, J.; Semenov, A.; Gol'tsman, G.; Hübers, H.-W.; Schwaab, G.; Voronov, B.; Gershenzon, E.
Title (down) Noise temperature of an NbN hot-electron bolometric mixer at frequencies from 0.7 THz to 5.2 THz Type Journal Article
Year 1999 Publication Supercond. Sci. Technol. Abbreviated Journal
Volume 12 Issue 11 Pages 748-750
Keywords NbN HEB mixers
Abstract We report on noise temperature measurements of an NbN phonon-cooled hot-electron bolometric mixer in the terahertz frequency range. The devices were 3 nm thick films with in-plane dimensions 1.7 × 0.2 µm2 and 0.9 × 0.2 µm2 integrated in a complementary logarithmic-spiral antenna. Measurements were performed at seven frequencies ranging from 0.7 THz to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 2600 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz) and 8800 K (5.2 THz).
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Call Number Serial 298
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