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Hajenius, M.; Yang, Z. Q.; Gao, J. R.; Baselmans, J. J. A.; Klapwijk, T. M.; Voronov, B.; Gol'tsman, G. |
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Title |
Optimized sensitivity of NbN hot electron bolometer mixers by annealing |
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Journal Article |
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Year |
2007 |
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IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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17 |
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2 |
Pages |
399-402 |
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Keywords |
NbN HEB mixers |
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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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1051-8223 |
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1426 |
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Baselmans, J. J. A.; Hajenius, M.; Gao, J. R.; Baryshev, A.; Kooi, J.; Klapwijk, T. M.; Voronov, B.; de Korte, P.; Gol'tsman, G. |
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Title |
NbN hot electron bolometer mixers: sensitivity, LO power, direct detection and stability |
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Journal Article |
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Year |
2005 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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15 |
Issue |
2 |
Pages |
484-489 |
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HEB mixers, direct detection effect, stability, Allan variance |
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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. Both the receiver noise temperature and the gain bandwidth can be improved by 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 of 950 K at 2.5 THz and 4.3 K, using a 0.4/spl times/4 /spl mu/m HEB mixer with a spiral antenna. At the same bias point, we obtain an IF gain bandwidth of 6 GHz. To comply with current demands on THz mixers for use in space based receivers we reduce the device size to 0.15/spl times/1 /spl mu/m and use a twin slot antenna. We report measurements of the noise temperature, LO power requirement, stability and the direct detection effect, using a mixer with a 1.6 THz twin slot antenna and a 1.462 THz solid state LO source with calibrated output power. |
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1051-8223 |
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546 |
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Hajenius, M.; Barends, R.; Gao, J. R.; Klapwijk, T. M.; Baselmans, J. J. A.; Baryshev, A.; Voronov, B.; Gol'tsman, G. |
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Title |
Local resistivity and the current-voltage characteristics of hot electron bolometer mixers |
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Journal Article |
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Year |
2005 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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15 |
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2 |
Pages |
495-498 |
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HEB mixer distributed model, HEB distributed model, distributed HEB model |
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Hot-electron bolometer devices, used successfully in low noise heterodyne mixing at frequencies up to 2.5 THz, have been analyzed. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, is used to model pumped IV curves and understand the physical conditions during the mixing process. We argue that the mixing is predominantly due to the strongly temperature dependent local resistivity of the NbN. Experimentally we identify the origins of different transition temperatures in a real HEB device, suggesting the importance of the intrinsic resistive transition of the superconducting bridge in the modeling. |
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1051-8223 |
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980 |
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Gao, J. R.; Hajenius, M.; Baselmans, J. J. A.; Yang, Z. Q.; Baryshev, A. M.; Barends, R.; Klapwijk, T. M.; Voronov, B.; Gol'tsman, G.; Callaos, N. |
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Title |
Twin-slot antenna coupled NbN hot electron bolometer mixers for space applications |
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Conference Article |
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2005 |
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Proc. 9-th WMSCI |
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Proc. 9-th WMSCI |
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9 |
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148-153 |
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Keywords |
NbN HEB mixers |
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International Institute of Informatics and Systemics |
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9806560639, 9789806560635 |
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9th World Multi-Conference on Systemics, Cybernetics and Informatics |
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1480 |
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Baselmans, J.; Kooi, J.; Baryshev, A.; Yang, Z. Q.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; Voronov, B.; Gol’tsman, G. |
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Title |
Full characterization of small volume NbN HEB mixers for space applications |
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Conference Article |
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2005 |
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Proc. 16th Int. Symp. Space Terahertz Technol. |
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Proc. 16th Int. Symp. Space Terahertz Technol. |
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457-462 |
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Keywords |
NbN HEB mixers |
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NbN phonon cooled HEB’s are one of the most promising bolometer mixer technologies for (near) future (space) applications. Their performance is usually quantified by mea- suring the receiver noise temperature at a given IF frequency, usually around 1 – 2 GHz. However, for any real applications it is vital that one fully knows all the relevant properties of the mixer, including LO power, stability, direct detection, gain bandwidth and noise bandwidth, not only the noise temperature at low IF frequencies. To this aim we have measured all these parameters at the optimal operating point of one single, small volume quasioptical NbN HEB mixer. We find a minimum noise temperature of 900 K at 1.46 THz. We observe a direct detection effect indicated by a change in bias current when changing from a 300 K hot load to a 77 K cold load. Due to this effect we overestimate the noise temperature by about 22% using a 300 K hot load and a 77 K cold load. The LO power needed to reach the optimal operating point is 80 nW at the receiver lens front, 59 nW inside the NbN bridge. However, using the isothermal technique we find a power absorbed in the NbN bridge of 25 nW, a difference of about a factor 2. We obtain a gain bandwidth of 2.3 GHz and a noise bandwidth of 4 GHz. The system Allan time is about 1 sec. in a 50 MHz spectral bandwidth and a deviation from white noise integration (governed by the radiometer equation) occurs at 0.2 sec., which implies a maximum integration time of a few seconds in a 1 MHz bandwidth spectrometer. |
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Göteborg, Sweden |
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363 |
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