| Records |
| Author |
Hübers, H.-W.; Schubert, J.; Krabbe, A.; Birk, M.; Wagner, G.; Semenov, A.; Gol’tsman, G.; Voronov, B.; Gershenzon, E. |
| Title |
Parylene anti-reflection coating of a quasi-optical hot-electron-bolometric mixer at terahertz frequencies |
Type |
Journal Article |
| Year |
2001 |
Publication |
Infrared Physics & Technology |
Abbreviated Journal |
Infrared Physics & Technology |
| Volume |
42 |
Issue  |
1 |
Pages |
41-47 |
| Keywords |
NbN HEB mixers, anti-reflection coating |
| Abstract |
Parylene C was investigated as anti-reflection coating for silicon at terahertz frequencies. Measurements with a Fourier-transform spectrometer show that the transmittance of pure silicon can be improved by about 30% when applying a layer of Parylene C with a quarter wavelength optical thickness. The 10% bandwidth of this coating extends from 1.5 to 3 THz for a center frequency of 2.3–2.5 THz, where the transmittance is constant. Heterodyne measurements demonstrate that the noise temperature of a hot-electron-bolometric mixer can be reduced significantly by coating the silicon lens of the hybrid antenna with a quarter wavelength Parylene C layer. Compared to the same mixer with an uncoated lens the improvement is about 30% at a frequency of 2.5 THz. |
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| ISSN |
1350-4495 |
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1548 |
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| Author |
Smirnov, K. V.; Ptitsina, N. G.; Vakhtomin, Y. B.; Verevkin, A. A.; Gol’tsman, G. N.; Gershenzon, E. M. |
| Title |
Energy relaxation of two-dimensional electrons in the quantum Hall effect regime |
Type |
Journal Article |
| Year |
2000 |
Publication |
JETP Lett. |
Abbreviated Journal |
JETP Lett. |
| Volume |
71 |
Issue |
1 |
Pages |
31-34 |
| Keywords |
2DEG, GaAs/AlGaAs heterostructures |
| Abstract |
The mm-wave spectroscopy with high temporal resolution is used to measure the energy relaxation times τe of 2D electrons in GaAs/AlGaAs heterostructures in magnetic fields B=0–4 T under quasi-equilibrium conditions at T=4.2 K. With increasing B, a considerable increase in τe from 0.9 to 25 ns is observed. For high B and low values of the filling factor ν, the energy relaxation rate τ −1e oscillates. The depth of these oscillations and the positions of maxima depend on the filling factor ν. For ν>5, the relaxation rate τ −1e is maximum when the Fermi level lies in the region of the localized states between the Landau levels. For lower values of ν, the relaxation rate is maximum at half-integer values of τ −1e when the Fermi level is coincident with the Landau level. The characteristic features of the dependence τ −1e (B) are explained by different contributions of the intralevel and interlevel electron-phonon transitions to the process of the energy relaxation of 2D electrons. |
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0021-3640 |
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http://jetpletters.ru/ps/899/article_13838.shtml (“Энергетическая релаксация двумерных электронов в области квантового эффекта Холла”) |
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1559 |
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Zorin, M.; Lindgren, M.; Danerud, M.; Karasik, B.; Winkler, D.; Gol'tsman, G.; Gershenzon, E. |
| Title |
Nonequilibrium and bolometric responses of YBaCuO thin films to high-frequency modulated laser radiation |
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Journal Article |
| Year |
1995 |
Publication |
J. Supercond. |
Abbreviated Journal |
J. Supercond. |
| Volume |
8 |
Issue |
1 |
Pages |
11-15 |
| Keywords |
YBCO HTS HEB |
| Abstract |
Picosecond nonequilibrium and slow bolometric responses to infrared radiation from a patterned high-T c superconducting (HTS) film in resistive and normal states deposited onto LaAlO3, NdGaO3, and MgO substrates were investigated using both pulse and modulation techniques. The response time of 35 ps to a laser pulse of 17 ps FWHM has been observed. The intrinsic response time of the fast process is expected to be about a few picoseconds. The modulation technique, being free from the disadvantages of pulse methods (poor sensitivity, limited dynamic range), makes the detailed study of a number of relaxation processes possible. Besides the nonequilibrium response, two kinds of bolometric processes, namely phonon transport through the film-substrate interface and phonon thermal diffusion in a substrate, manifest themselves in certain frequency dependences. |
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0896-1107 |
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no |
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1630 |
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Nebosis, R. S.; Heusinger, M. A.; Schatz, W.; Renk, K. F.; Gol’tsman, G. N.; Karasik, B. S.; Semenov, A. D.; Gershenzon, E. M. |
| Title |
Ultrafast photoresponse of a structured YBa2Cu3O7-δ thin film to ultrashort FIR laser pulses |
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Journal Article |
| Year |
1993 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
3 |
Issue |
1 |
Pages |
2160-2162 |
| Keywords |
YBCO HTS detectors |
| Abstract |
The authors have investigated the photoinduced voltage response of a current-carrying structured YBa2Cu3O7-δ thin film to ultrashort far-infrared (FIR) laser pulses in the frequency range from 0.7 THz to 7 THz. The detector has shown an almost constant sensitivity of 1 mV/W and a noise equivalent power of less than 5*10/sup -7/ W/ square root Hz. The temperature dependence of the decay time of the detector signal was studied for temperatures around the transition temperature of the film ( approximately 80 K). For a detector temperature where dR/dT had its maximum, the authors observed bolometric signals with decay times of about 2 ns, and for lower temperatures they observed nonbolometric signals with decay times of approximately 120 ps; the duration of the nonbolometric signals was limited by the time resolution of the electronic registration equipment. |
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1658 |
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Semenov, A. D.; Goghidze, I. G.; Gol’tsman, G. N.; Sergeev, A. V.; Aksaev, E. E.; Gershenzon, E. M. |
| Title |
Non-equilibrium quasiparticle response to radiation and bolometric effect in YBaCuO films |
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Journal Article |
| Year |
1993 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
3 |
Issue |
1 |
Pages |
2132-2135 |
| Keywords |
YBCO HTS HEB detectors |
| Abstract |
The voltage photoresponse of structured current biased YBCO films on different substrates to 20-ps laser pulses of 0.63- mu m and 1.54- mu m wavelengths and to continuously modulated radiation of 2-mm wavelength is measured to temperatures around Tc. Fast picosecond decay of the response to pulsed radiation is followed by slow exponential relaxation with a nanosecond characteristic time depending on the substrate material and film dimensions. The slow component does not depend on wavelength and is attributed to the bolometric effect, while the magnitude of the fast component associated with nonequilibrium response rises with wavelength. More than an order-of-magnitude increase of the nonequilibrium response is seen from near-infrared to millimeter-wave range. This dependence plausibly reflects the low efficiency of multiplication of photoexcited electrons in YBaCuO compared to conventional superconductors. |
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1558-2515 |
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no |
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1659 |
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Gershenzon, E. M.; Gol'tsman, G. N.; Ptitsina, N. G. |
| Title |
Investigation of free excitons in Ge and their condensation at submillimeter wavelengths |
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Journal Article |
| Year |
1976 |
Publication |
Sov. Phys. JETP |
Abbreviated Journal |
Sov. Phys. JETP |
| Volume |
43 |
Issue |
1 |
Pages |
116-122 |
| Keywords |
Ge, free excitons |
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Results are presented of an investigation of free excitons in Ge in the submillimeter wavelength range for low as well as for high excitation levels when interaction between the excitons becomes important. The free-exciton energy spectrum is discussed. It is shown that the drop radii and their concentrations can be determined by measuring the temperature dependence of the free-exciton concentration. A section of the phase diagram is obtained in the 0.5-2.8 K temperature range for the free excitons+condensate system. |
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no |
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1731 |
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Mel’nikov, A. P.; Gurvich, Y. A.; Shestakov, L. N.; Gershenzon, E. M. |
| Title |
Magnetic field effects on the nonohmic impurity conduction of uncompensated crystalline silicon |
Type |
Journal Article |
| Year |
2001 |
Publication |
Jetp Lett. |
Abbreviated Journal |
Jetp Lett. |
| Volume |
73 |
Issue |
1 |
Pages |
44-47 |
| Keywords |
uncompensated crystalline silicon, nonohmic impurity conduction, magnetic field |
| Abstract |
The impurity conduction of a series of crystalline silicon samples with the concentration of major impurity N ≈ 3 × 1016 cm−3 and with a varied, but very small, compensation K was measured as a function of the electric field E in various magnetic fields H-σ(H, E). It was found that, at K < 10−3 and in moderate E, where these samples are characterized by a negative nonohmicity (dσ(0, E)/dE < 0), the ratio σ(H, E)/σ(0, E) > 1 (negative magnetoresistance). With increasing E, these inequalities are simultaneously reversed (positive nonohmicity and positive magnetoresistance). It is suggested that both negative and positive nonohmicities are due to electron transitions in electric fields from impurity ground states to states in the Mott-Hubbard gap. |
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0021-3640 |
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no |
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1752 |
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Gershenzon, E. M.; Goltsman, G. N.; Semenov, A. D.; Sergeev, A. V. |
| Title |
Limiting characteristic of fast superconducting bolometers |
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Journal Article |
| Year |
1989 |
Publication |
Sov. Phys.-Tech. Phys. |
Abbreviated Journal |
Sov. Phys.-Tech. Phys. |
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34 |
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195-199 |
| Keywords |
HEB |
| Abstract |
Теоретически и экспериментально исследовано физическое ограничение быстродействия сверхпроводящего болометра. Показано, что минимальная постоянная времени реализуется в условиях электронного разогрева и определяется процессом неупругого электрон-фонон- ного взаимодействия. Сформулированы требования кконструкции «электронного болометра» для достижения предельной чувствительности. Проведено сравнение характеристик электронного болометра и обычных болометров различных типов. |
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О предельных характеристиках быстродействующих серхпроводниковых болометров |
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237 |
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Yagubov, P.; Gol'tsman, G.; Voronov, B.; Seidman, L.; Siomash, V.; Cherednichenko, S.; Gershenzon, E. |
| Title |
The bandwidth of HEB mixers employing ultrathin NbN films on sapphire substrate |
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Conference Article |
| Year |
1996 |
Publication |
Proc. 7th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 7th Int. Symp. Space Terahertz Technol. |
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Issue |
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Pages |
290-302 |
| Keywords |
NbN HEB mixers, fabrication process |
| Abstract |
We report on some unusual features observed during fabrication of ultrathin NbN films with high Tc. The films were used to fabricate HEB mixers, which were evaluated for IF bandwidth measurements at 140 GHz. Ultrathin films were fabricated using reactive dc magnetron sputtering with a discharge current source. Reproducible parameters of the films are assured keeping constant the difference between the discharge voltage in pure argon, and in a gas mixture, for the same current. A maximum bandwidth of 4 GHz at optimal LO and dc bias was obtained for mixer chip based on NbN film 35 A thick with Tc = 11 K. |
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Charlottesville, Virginia, USA |
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266 |
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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 |
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Conference Article |
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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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