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Author Hajenius, M.; Yang, Z. Q.; Gao, J. R.; Baselmans, J. J. A.; Klapwijk, T. M.; Voronov, B.; Gol'tsman, G.
Title Optimized sensitivity of NbN hot electron bolometer mixers by annealing Type Journal Article
Year 2007 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume (up) 17 Issue 2 Pages 399-402
Keywords NbN HEB mixers
Abstract We report that the heterodyne sensitivity of superconducting hot-electron bolometers (HEBs) increases by 25-30% after annealing at 85degC in high vacuum. The devices studied are twin-slot antenna coupled mixers with a small area NbN bridge of 1 mum times 0.15 mum, above which there is a SiO 2 passivation layer. The mixer noise temperature, gain, and resistance versus temperature curve of a HEB before and after annealing are compared and analysed. We show that the annealing reduces the intrinsic noise of the mixer by 37% and makes the superconducting transition of the bridge and the contacts sharper. We argue that the reduction ofthe noise is mainly due to the improvement of the transparency of the contact/film interface. The lowest receiver noise temperature of 700 K is measured at a local oscillator frequency of 1.63 THz and at a bath temperature of 4.2 K.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1051-8223 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1426
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Author Yang, Z. Q.; Hajenius, M.; Baselmans, J. J. A.; Gao, J. R.; Voronov, B.; Gol’tsman, G. N.
Title Reduced noise in NbN hot-electron bolometer mixers by annealing Type Journal Article
Year 2006 Publication Supercond. Sci. Technol. Abbreviated Journal Supercond. Sci. Technol.
Volume (up) 19 Issue 4 Pages L (9 to 12)
Keywords NbN HEB mixers
Abstract We find that the sensitivity of heterodyne receivers based on superconducting hot-electron bolometers (HEBs) increases by 25–30% after annealing at 85 °C in vacuum. The devices studied are twin-slot antenna coupled mixers with a small NbN bridge of 1 × 0.15 µm2. We show that annealing changes the device properties as reflected in sharper resistive transitions of the complete device, apparently reducing the device-related noise. The lowest receiver noise temperature of 700 K is measured at a local oscillator frequency of 1.63 THz and a bath temperature of 4.3 K.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0953-2048 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1456
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Author Floet, D. Wilms; Baselmans, J. J. A.; Klapwijk, T. M.; Gao, J. R.
Title Resistive transition of niobium superconducting hot-electron bolometer mixers Type Journal Article
Year 1998 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.
Volume (up) 73 Issue 19 Pages 2826
Keywords HEB
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-6951 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 543
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Author Baselmans, J. J. A.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; de Korte, P. A. J.; Voronov, B.; Gol'tsman, G.
Title Doubling of sensitivity and bandwidth in phonon cooled hot electron bolometer mixers Type Journal Article
Year 2004 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.
Volume (up) 84 Issue 11 Pages 1958-1960
Keywords NbN HEB mixers
Abstract We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. We show experimentally that both the receiver noise temperature and the gain bandwidth can be improved by more than a factor of 2 by cleaning the interface and adding an additional superconducting interlayer to the contact pad. Using this we obtain a double sideband receiver noise temperature TN,DSB=950 K

at 2.5 THz and 4.3 K, uncorrected for losses in the optics. At the same bias point, we obtain an IF gain bandwidth of 6 GHz.
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Notes Approved no
Call Number Serial 352
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Author Baselmans, J. J. A.; Baryshev, A.; Reker, S. F.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; Vahtomin, Yu.; Maslennikov, S.; Antipov, S.; Voronov, B.; Gol'tsman, G.
Title Direct detection effect in small volume hot electron bolometer mixers Type Journal Article
Year 2005 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.
Volume (up) 86 Issue 16 Pages 163503 (1 to 3)
Keywords HEB, mixer, direct detection effect
Abstract We measure the direct detection effect in a small volume (0.15μm×1μm×3.5nm)(0.15μm×1μm×3.5nm) quasioptical NbN phonon cooled hot electronbolometermixer at 1.6THz1.6THz. We find that the small signal sensitivity of the receiver is underestimated by 35% due to the direct detection effect and that the optimal operating point is shifted to higher bias voltages when using calibration loads of 300K300K and 77K77K. Using a 200GHz200GHzbandpass filter at 4.2K4.2K the direct detection effect virtually disappears. This has important implications for the calibration procedure of these receivers in real telescope systems.
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Series Editor Series Title Abbreviated Series Title
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Area Expedition Conference
Notes Approved no
Call Number Serial 377
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