Records |
Author |
Il'in, K. S.; Gol'tsman, G. N.; Voronov, B. M.; Sobolewski, Roman |
Title |
Characterization of the electron energy relaxation process in NbN hot-electron devices |
Type |
Conference Article |
Year |
1999 |
Publication |
Proc. 10th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 10th Int. Symp. Space Terahertz Technol. |
Volume |
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Issue |
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Pages |
390-397 |
Keywords |
HEB mixers, SSPD, SNSPD, NbN films, Nb films |
Abstract |
We report on transient measurements of electron energy relaxation in NbN films with 300-fs time resolution. Using an electro-optic sampling technique, we have studied the photoresponse of 3.5-nm-thick NbN films deposited on sapphire substrates and exposed to 100-fs-wide optical pulses. Our experimental data analysis was based on the two-temperature model and has shown that in our films at the superconducting transition 10.5 K the inelastic electron-phonon scattering time was about (111}+-__.2) ps. This response time indicated that the maximum intermediate-frequency band of a NbN hot-electron phonon-cooled mixer should reach (16+41-3) GHz if one eliminates the bolometric phonon-heating effect. We have suggested several ways to increase the effectiveness of phonon cooling to achieve the above intrinsic value of the NbN mixer bandwidth. |
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1576 |
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Author |
Il'in, K. S.; Lindgren, M.; Currie, M. A.; Semenov, D.; Gol'tsman, G. N.; Sobolewski, Roman; Cherednichenko, S. I.; Gershenzon, E. M. |
Title |
Picosecond hot-electron energy relaxation in NbN superconducting photodetectors |
Type |
Journal Article |
Year |
2000 |
Publication |
Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
Volume |
76 |
Issue |
19 |
Pages |
2752-2754 |
Keywords |
NbN HEB detectors, two-temperature model, IF bandwidth |
Abstract |
We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron–phonon scattering time Ï„e–ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time Ï„es decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, Ï„e–ph and Ï„es, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of Ï„e–ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/–3) GHz if one eliminates the bolometric phonon-heating effect. |
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0003-6951 |
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856 |
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Author |
Il'in, K. S.; Verevkin, A. A.; Gol'tsman, G. N.; Sobolewski, R. |
Title |
Infrared hot-electron NbN superconducting photodetectors for imaging applications |
Type |
Journal Article |
Year |
1999 |
Publication |
Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
Volume |
12 |
Issue |
11 |
Pages |
755-758 |
Keywords |
NbN SSPD, SNSPD |
Abstract |
We report an effective quantum efficiency of 340, responsivity >200 A W-1 (>104 V W-1) and response time of 27±5 ps at temperatures close to the superconducting transition for NbN superconducting hot-electron photodetectors (HEPs) in the near-infrared and optical ranges. Our studies were performed on a few nm thick NbN films deposited on sapphire substrates and patterned into µm-size multibridge detector structures, incorporated into a coplanar transmission line. The time-resolved photoresponse was studied by means of subpicosecond electro-optic sampling with 100 fs wide laser pulses. The quantum efficiency and responsivity studies of our photodetectors were conducted using an amplitude-modulated infrared beam, fibre-optically coupled to the device. The observed picosecond response time and the very high efficiency and sensitivity of the NbN HEPs make them an excellent choice for infrared imaging photodetectors and input optical-to-electrical transducers for superconducting digital circuits. |
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0953-2048 |
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1562 |
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Author |
Il'in, K.; Siegel, M.; Semenov, A.; Engel, A.; Hübers, H.-W.; Hollmann, E.; Gol'tsman, G.; Voronov, B. |
Title |
Thickness dependence of superconducting properties of ultrathin Nb and NbN films |
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Conference Article |
Year |
2004 |
Publication |
AKF-Frühjahrstagung |
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Keywords |
Nb, NbN films, has potential plagiarism |
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Berlin-Adlershof |
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1503 |
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Il’in, K. S.; Milostnaya, I. I.; Verevkin, A. A.; Gol’tsman, G. N.; Gershenzon, E. M.; Sobolewski, R. |
Title |
Ultimate quantum efficiency of a superconducting hot-electron photodetector |
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Journal Article |
Year |
1998 |
Publication |
Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
Volume |
73 |
Issue |
26 |
Pages |
3938-3940 |
Keywords |
NbN SSPD, SNSPD |
Abstract |
The quantum efficiency and current and voltage responsivities of fast hot-electron photodetectors, fabricated from superconducting NbN thin films and biased in the resistive state, have been shown to reach values of 340, 220 A/W, and 4×104 V/W,
respectively, for infrared radiation with a wavelength of 0.79 μm. The characteristics of the photodetectors are presented within the general model, based on relaxation processes in the nonequilibrium electron heating of a superconducting thin film. The observed, very high efficiency and sensitivity of the superconductor absorbing the photon are explained by the high multiplication rate of quasiparticles during the avalanche breaking of Cooper pairs. |
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0003-6951 |
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1579 |
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