Records |
Author |
Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Goltsman, G. N.; Verevkin, A. A.; Toropov, A. I.; Mauskopf, P. |
Title |
Concentration dependence of energy relaxation time in AlGaAs/GaAs heterojunctions: direct measurements |
Type |
Journal Article |
Year |
2011 |
Publication |
Semicond. Sci. Technol. |
Abbreviated Journal |
Semicond. Sci. Technol. |
Volume |
26 |
Issue |
2 |
Pages |
025013 |
Keywords |
AlGaAs/GaAs heterojunctions |
Abstract |
We present measurements of the energy relaxation time, τε, of electrons in a single heterojunction in a quasi-equilibrium state using microwave time-resolved spectroscopy at 4.2 K. We find the relaxation time has a power-law dependence on the carrier density of the two-dimensional electron gas, τε∝nγs with γ = 0.40 ± 0.02 for values of the carrier density, ns, from 1.6 × 1011 to 6.6 × 1011cm−2. The results are in good agreement with predictions taking into account the scattering of the carriers by both piezoelectric and deformation potential acoustic phonons. We compare these results with indirect measurements of the energy relaxation time from energy loss measurements involving Joule heating of the electron gas. |
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0268-1242 |
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Call Number |
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Serial |
1215 |
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Author |
Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol'tsman, G. |
Title |
One-dimensional resistive states in quasi-two-dimensional superconductors |
Type |
Journal Article |
Year |
2007 |
Publication |
arXiv:0709.0709v1 [cond-mat.supr-con] |
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Volume |
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Issue |
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Pages |
1-11 |
Keywords |
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Abstract |
We investigate competition between one- and two-dimensional topological excitations – phase slips and vortices – in formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature T(C0). The widths w = 100 nm of our ultrathin NbN samples is substantially larger than the Ginzburg-Landau coherence length ξ = 4nm and the fluctuation resistivity above T(C0) has a two-dimensional character. However, our data shows that the resistivity below T(C0) is produced by one-dimensional excitations, – thermally activated phase slip strips (PSSs) overlapping the sample cross-section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current/temperature variations. Measuring the resistivity within seven orders of magnitude, we find that the quantum phase slips can only be essential below this level. |
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RPLAB @ atomics90 @ |
Serial |
948 |
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Author |
Verevkin, A.; Zhang, J.; Slysz, W.; Sobolewski, Roman; Lipatov, A.; Okunev, O.; Chulkova, G.; Korneev, A.; Smimov, K.; Gol'tsman, G. N. |
Title |
Spectral sensitivity and temporal resolution of NbN superconducting single-photon detectors |
Type |
Conference Article |
Year |
2002 |
Publication |
Proc. 13th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 13th Int. Symp. Space Terahertz Technol. |
Volume |
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Issue |
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Pages |
105-111 |
Keywords |
NbN SSPD, SNSPD |
Abstract |
We report our studies on spectral sensitivity and time resolution of superconducting NbN thin film single-photon detectors (SPDs). Our SPDs exhibit an everimentally measured detection efficiencies (DE) from — 0.2% at 2=1550 nm up to —3% at lambda=405 nm wavelength for 10-nm film thickness devices and up to 3.5% at lambda=1550 nm for 3.5-nm film thickness devices. Spectral dependences of detection efficiency (DE) at 2=0.4 —3.0 pm range are presented. With variable optical delay setup, it is shown that NbN SPD potentially can resolve optical pulses with the repetition rate up to 10 GHz at least. The observed full width at the half maximum (FWHM) of the signal pulse is about 150-180 ps, limited by read-out electronics. The jitter of NbN SPD is measured to be —35 ps at optimum biasing. |
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1528 |
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Author |
Bell, M.; Kaurova, N.; Divochiy, A.; Gol'tsman, G.; Bird, J.; Sergeev, A.; Verevkin, A. |
Title |
On the nature of resistive transition in disordered superconducting nanowires |
Type |
Journal Article |
Year |
2007 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
Volume |
17 |
Issue |
2 |
Pages |
267-270 |
Keywords |
SSPD, SNSPD |
Abstract |
Hot-electron single-photon counters based on long superconducting nanowires are starting to become popular in optical and infrared technologies due to their ultimately high sensitivity and very high response speed. We investigate intrinsic fluctuations in long NbN nanowires in the temperature range of 4.2 K-20 K, i.e. above and below the superconducting transition. These fluctuations are responsible for fluctuation resistivity and also determine the noise in practical devices. Measurements of the fluctuation resistivity were performed at low current densities and also in external magnetic fields up to 5 T. Above the BCS critical temperature T co the resistivity is well described by the Aslamazov-Larkin (AL) theory for two-dimensional samples. Below T co the measured resistivity is in excellent agreement with the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory developed for one-dimensional superconductors. Despite that our nanowires of 100 nm width are two-dimensional with respect to the coherence length, our analysis shows that at relatively low current densities the one-dimensional LAMH mechanism based on thermally induced phase slip centers dominates over the two-dimensional mechanism related to unbinding of vortex-antivortex pairs below the Berezinskii-Kosterlitz-Thouless transition. |
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1051-8223 |
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no |
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1247 |
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Author |
Kitaygorsky, J.; Zhang, J.; Verevkin, A.; Sergeev, A.; Korneev, A.; Matvienko, V.; Kouminov, P.; Smirnov, K.; Voronov, B.; Gol'tsman, G.; Sobolewski, R. |
Title |
Origin of dark counts in nanostructured NbN single-photon detectors |
Type |
Journal Article |
Year |
2005 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
Volume |
15 |
Issue |
2 |
Pages |
545-548 |
Keywords |
SSPD dark counts, SNSPD, dark counts rate |
Abstract |
We present our study of dark counts in ultrathin (3.5 to 10 nm thick), narrow (120 to 170 nm wide) NbN superconducting stripes of different lengths. In experiments, where the stripe was completely isolated from the outside world and kept at temperature below the critical temperature Tc, we detected subnanosecond electrical pulses associated with the spontaneous appearance of the temporal resistive state. The resistive state manifested itself as generation of phase-slip centers (PSCs) in our two-dimensional superconducting stripes. Our analysis shows that not far from Tc, PSCs have a thermally activated nature. At lowest temperatures, far below Tc, they are created by quantum fluctuations. |
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no |
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Serial |
1057 |
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Author |
Zhang, Jin; Slysz, W.; Verevkin, A.; Okunev, O.; Chulkova, G.; Korneev, A.; Lipatov, A.; Gol'tsman, G. N.; Sobolewski, R. |
Title |
Response time characterization of NbN superconducting single-photon detectors |
Type |
Journal Article |
Year |
2003 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
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Volume |
13 |
Issue |
2 |
Pages |
180-183 |
Keywords |
SSPD jitter, SNSPD jitter |
Abstract |
We report our time-resolved measurements of NbN-based superconducting single-photon detectors. The structures are meander-type, 10-nm thick, and 200-nm wide stripes and were operated at 4.2 K. We have shown that the NbN devices can count single-photon pulses with below 100-ps time resolution. The response signal pulse width was about 150 ps, and the system jitter was measured to be 35 ps. |
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IEEE |
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no |
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1058 |
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Author |
Skalare, A.; McGrath, William R.; Echternach, P. M.; Leduc, H. G.; Siddiqi, I.; Verevkin, A.; Prober, D. E. |
Title |
Aluminum hot-electron bolometer mixers at submillimeter wavelengths |
Type |
Journal Article |
Year |
2001 |
Publication |
IEEE Trans. Appl. Supercond. |
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Volume |
11 |
Issue |
1 |
Pages |
641-644 |
Keywords |
Al HEB mixer, contacts, interface, in situ, in-situ, Aluminium HEB mixer |
Abstract |
Diffusion-cooled aluminum hot-electron bolometer (HEB) mixers are of interest for low-noise high resolution THz-frequency spectroscopy within astrophysics. Al HEB mixers offer operation with an order of magnitude less local oscillator power, higher intermediate frequency bandwidth and potentially lower noise than competing devices made from other materials. We report on mixer experiments at 618 GHz with devices fabricated from films with sheet resistances in the range from about 55 Ω down to about 9 Ω per square. Intermediate frequency bandwidths of up to 3 GHz were measured (1 μm long device), with absorbed local oscillator power levels of 0.5 to 6 nW and mixer conversion up to -21.5 dB. High input coupling efficiency implies that the electrons in the device are able to thermalize before escaping from the device. It was found that the long coherence length complicates mixer operations due to the proximity of the contact pads. Also, saturation at the IF frequency may be a concern for this type of device, and warrants further studies. |
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1051-8223 |
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no |
Call Number |
ref919426b |
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1061 |
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Author |
Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Gol’tsman, G. N.; Verevkin, A. A.; Toropov, A. I. |
Title |
Frequency bandwidth and conversion loss of a semiconductor heterodyne receiver with phonon cooling of two-dimensional electrons |
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Journal Article |
Year |
2010 |
Publication |
Semicond. |
Abbreviated Journal |
Semicond. |
Volume |
44 |
Issue |
11 |
Pages |
1427-1429 |
Keywords |
2DEG, AlGaAs/GaAs heterostructures mixers |
Abstract |
The temperature and concentration dependences of the frequency bandwidth of terahertz heterodyne AlGaAs/GaAs detectors based on hot electron phenomena with phonon cooling of two-dimensional electrons have been measured by submillimeter spectroscopy with a high time resolution. At a temperature of 4.2 K, the frequency bandwidth at a level of 3 dB (f 3 dB) is varied from 150 to 250 MHz with a change in the concentration n s according to the power law f 3dB ∝ n −0.5 s due to the dominant contribution of piezoelectric phonon scattering. The minimum conversion loss of the semiconductor heterodyne detector is obtained in structures with a high carrier mobility (μ > 3 × 105 cm2 V−1 s−1 at 4.2 K). |
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1063-7826 |
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Полоса и потери преобразования полупроводникового смесителя с фононным каналом охлаждения двумерных электронов |
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no |
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1216 |
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Author |
Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Gol’tsman, G. N.; Verevkin, A. A.; Toropov, A. I. |
Title |
Concentration dependence of the intermediate frequency bandwidth of submillimeter heterodyne AlGaAs/GaAs nanostructures |
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Journal Article |
Year |
2010 |
Publication |
Bull. Russ. Acad. Sci. Phys. |
Abbreviated Journal |
Bull. Russ. Acad. Sci. Phys. |
Volume |
74 |
Issue |
1 |
Pages |
100-102 |
Keywords |
2DEG AlGaAs/GaAs heterostructures, THz heterodyne detectors, IF bandwidth |
Abstract |
The concentration dependence of the intermediate frequency bandwidth of heterodyne AlGaAs/GaAs detectors with 2D electron gas is measured using submillimeter spectroscopy with high time resolution at T= 4.2 K. The intermediate frequency bandwidth f3dBfalls from 245 to 145 MHz with increasing concentration of 2D electrons n s = (1.6-6.6) × 10[su11] cm-2. The dependence f3dB ≈ n s – 0.04±is observed in the studied concentration range; this dependence is determined by electron scattering by the deformation potential of acoustic phonons and piezoelectric scattering. |
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1062-8738 |
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no |
Call Number |
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Serial |
1217 |
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Author |
Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol’tsman, G. |
Title |
One-dimensional resistive states in quasi-two-dimensional superconductors: Experiment and theory |
Type |
Journal Article |
Year |
2007 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
76 |
Issue |
9 |
Pages |
094521 (1 to 5) |
Keywords |
uasi-two-dimensional superconductors, NbN |
Abstract |
We investigate competition between one- and two-dimensional topological excitations—phase slips and vortices—in the formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature TC0. The widths w=100nm of our ultrathin NbN samples are substantially larger than the Ginzburg-Landau coherence length ξ=4nm, and the fluctuation resistivity above TC0 has a two-dimensional character. However, our data show that the resistivity below TC0 is produced by one-dimensional excitations—thermally activated phase slip strips (PSSs) overlapping the sample cross section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current and/or temperature variations. Measuring the resistivity within 7 orders of magnitude, we find that the quantum phase slips can only be essential below this level. |
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1098-0121 |
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Call Number |
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1423 |
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