| Records |
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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Il'in, K. S.; Cherednichenko, S. I.; Gol'tsman, G. N.; Currie, M.; Sobolewski, R. |
| Title |
Comparative study of the bandwidth of phonon-cooled NbN hot-electron bolometers in submillimeter and optical wavelength ranges |
Type |
Conference Article |
| Year |
1998 |
Publication |
Proc. 9th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 9th Int. Symp. Space Terahertz Technol. |
| Volume |
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Issue |
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Pages |
323-330 |
| Keywords |
NbN HEB mixers |
| Abstract |
We report the results of the bandwidth measurements of NbN hot-electron bolometers, perfomied in the terahertz frequency domain at 140 GHz and 660 GHz and in time domain in the optical range at the wavelength of 395 nm.. Our studies were done on 3.5-nm-thick NbN films evaporated on sapphire substrates and patterned into ilin-size microbridges. In order to measure the gain bandwidth, we used two identical BWOs (140 or 660 GHz), one functioning as a local oscillator and the other as a signal source. The bandwidth we achieved was 3.5-4 GHz at 4.2 K with the optimal LO and DC biases. Time-domain measurements with a resolution below 300 fs were performed using an electro-optic sampling system, in the temperature range between 4.2 K to 9 K at various values of the bias current and optical power. The obtained response time of the NbN hot-electron bolometer to —100- fs-wide Ti:sapphire laser pulses was about 27 ps, what corresponds to the 5.9 GHz gain bandwidth. |
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1590 |
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Gerecht, E.; Musante, C. F.; Wang, Z.; Yngvesson, K. S.; Waldman, J.; Gol'tsman, G. N.; Yagoubov, P. A.; Svechnikov, S. I.; Voronov, B. M.; Cherednichenko, S. I.; Gershenzon, E. M. |
| Title |
NbN hot electron bolometric mixer for 2.5 THz: the phonon cooled version |
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Conference Article |
| Year |
1997 |
Publication |
Proc. 8th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 8th Int. Symp. Space Terahertz Technol. |
| Volume |
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Issue |
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Pages |
258-271 |
| Keywords |
NbN HEB mixers |
| Abstract |
We describe an investigation of a NbN HEB mixer for 2.5 THz. NbN HEBs are phonon-cooled de-. vices which are expected, according to theory, to achieve up to 10 GHz IF conversion gain bandwidth. We have developed an antenna coupled device using a log-periodic antenna and a silicon lens. We have demon- strated that sufficient LO power can be coupled to the device in order to bring it to the optimum mixer oper- ating point. The LO power required is less than 1 microwatts as measured directly at the device. We also describe the impedance characteristics of NbN devices and compare them with theory. The experimental results agree with theory except for the imaginary part of the impedance at very low frequencies as was demonstrated by other groups. |
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1605 |
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| Author |
Cherednichenko, S.; Yagoubov, P.; Il'In, K.; Gol'tsman, G.; Gershenzon, E. |
| Title |
Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers on sapphire substrates |
Type |
Conference Article |
| Year |
1997 |
Publication |
Proc. 8th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 8th Int. Symp. Space Terahertz Technol. |
| Volume |
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Issue |
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Pages |
245-257 |
| Keywords |
NbN HEB mixers, fabrication process |
| Abstract |
The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 mm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 1.1 wide and 211 long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.5 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature. |
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276 |
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| Author |
Cherednichenko, S.; Yagoubov, P.; Il'in, K.; Gol'tsman, G.; Gershenzon, E. |
| Title |
Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers |
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Conference Article |
| Year |
1997 |
Publication |
Proc. 27th Eur. Microwave Conf. |
Abbreviated Journal |
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2 |
Issue |
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Pages |
972-977 |
| Keywords |
HEB mixer, fabrication process |
| Abstract |
The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 nm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 um wide and 2 um long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.2 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature. |
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Jerusalem, Israel |
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IEEE |
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27th Eur. Microwave Conf. |
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1075 |
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