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Author Annunziata, Anthony J.; Quaranta, Orlando; Santavicca, Daniel F.; Casaburi, Alessandro; Frunzio, Luigi; Ejrnaes, Mikkel; Rooks, Michael J.; Cristiano, Roberto; Pagano, Sergio; Frydman, Aviad; Prober, Daniel E.
Title Reset dynamics and latching in niobium superconducting nanowire single-photon detectors Type Journal Article
Year 2010 Publication J. Appl. Phys. Abbreviated Journal
Volume 108 Issue 8 Pages (up) 7
Keywords SNSPD
Abstract We study the reset dynamics of niobium (Nb) superconducting nanowire single-photon detectors (SNSPDs) using experimental measurements and numerical simulations. The numerical simulations of the detection dynamics agree well with experimental measurements, using independently determined parameters in the simulations. We find that if the photon-induced hotspot cools too slowly, the device will latch into a dc resistive state. To avoid latching, the time for the hotspot to cool must be short compared to the inductive time constant that governs the resetting of the current in the device after hotspot formation. From simulations of the energy relaxation process, we find that the hotspot cooling time is determined primarily by the temperature-dependent electron-phonon inelastic time. Latching prevents reset and precludes subsequent photon detection. Fast resetting to the superconducting state is, therefore, essential, and we demonstrate experimentally how this is achieved. We compare our results to studies of reset and latching in niobium nitride SNSPDs.
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Call Number RPLAB @ gujma @ Serial 649
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Author Semenov, A.; Engel, A.; Il'in, K.; Gol'tsman, G.; Siegel, M.; Hübers, H.-W.
Title Ultimate performance of a superconducting quantum detector Type Journal Article
Year 2003 Publication Eur. Phys. J. Appl. Phys. Abbreviated Journal Eur. Phys. J. Appl. Phys.
Volume 21 Issue 3 Pages (up) 171-178
Keywords NbN SSPD, SNSPD
Abstract We analyze the ultimate performance of a superconducting quantum detector in order to meet requirements for applications in near-infrared astronomy and X-ray spectroscopy. The detector exploits a combined detection mechanism, in which avalanche quasiparticle multiplication and the supercurrent jointly produce a voltage response to a single absorbed photon via successive formation of a photon-induced and a current-induced normal hotspot in a narrow superconducting strip. The response time of the detector should increase with the photon energy providing energy resolution. Depending on the superconducting material and operation conditions, the cut-off wavelength for the single-photon detection regime varies from infrared waves to visible light. We simulated the performance of the background-limited infrared direct detector and X-ray photon counter utilizing the above mechanism. Low dark count rate and intrinsic low-frequency cut-off allow for realizing a background limited noise equivalent power of 10−20 W Hz−1/2 for a far-infrared direct detector exposed to 4-K background radiation. At low temperatures, the intrinsic response time of the counter is rather determined by diffusion of nonequilibrium electrons than by the rate of energy transfer to phonons. Therefore, thermal fluctuations do not hamper energy resolution of the X-ray photon counter that should be better than 10−3 for 6-keV photons. Comparison of new data obtained with a Nb based detector and previously reported results on NbN quantum detectors support our estimates of ultimate detector performance.
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ISSN 1286-0042 ISBN Medium
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Notes Approved no
Call Number Serial 534
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Author Semenov, A. D.; Gol’tsman, G. N.
Title Nonthermal mixing mechanism in a diffusion-cooled hot-electron detector Type Journal Article
Year 2000 Publication J. Appl. Phys. Abbreviated Journal J. Appl. Phys.
Volume 87 Issue 1 Pages (up) 502-510
Keywords NbN HEB mixers, nonthermal
Abstract We present an analysis of a diffusion-cooled hot-electron detector fabricated from clean superconducting material with low transition temperature. The distinctive feature of a clean material, i.e., material with large electron mean free path, is a relatively weak inelastic electron scattering that is not sufficient for the establishment of an elevated thermodynamic electron temperature when the detector is subjected to irradiation. We propose an athermal model of a diffusion-cooled detector that relies on suppression of the superconducting energy gap by the actual dynamic distribution of excess quasiparticles. The resistive state of the device is caused by the electric field penetrating into the superconducting bridge from metal contacts. The dependence of the penetration length on the energy gap delivers the detection mechanism. The sources of the electric noise are equilibrium fluctuations of the number of thermal quasiparticles and frequency dependent shot noise. Using material parameters typical for A1, we evaluate performance of the device in the heterodyne regime at terahertz frequencies. Estimates show that the mixer may have a noise temperature of a few quantum limits and a bandwidth of a few tens of GHz, while the required local oscillator power is in the μW range due to ineffective suppression of the energy gap by quasiparticles with high energies.
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ISSN 0021-8979 ISBN Medium
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Notes Approved no
Call Number Serial 1558
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Author Uchiki, Hisao; Kobayashi, Takayoshi; Sakaki, Hiroyuki
Title Photoluminescence and energy‐loss rates in GaAs quantum wells under high‐density excitation Type Journal Article
Year 1987 Publication J. Appl. Phys. Abbreviated Journal
Volume 62 Issue 3 Pages (up) 1010-1016
Keywords 2DEG, GaAs/AlGaAs, heat flow, electron-phonon, hole-phonon, carrier-phonon, interactions
Abstract The time‐resolved luminescence spectra from excited conduction subbands in three samples of multi‐quantum‐well GaAs/AlxGa1-xAs (x=0.3 and 1) semiconductors with several well widths and barrier heights were obtained under high‐density excitations by a 30‐ps pulsed laser at 532 nm, which generated electron–hole pairs to the concentration of 1010–1013/cm2 per well per pulse at 77 K. The temperature and the Fermi energy of electron were determined by fitting best the constructed time‐resolved spectrum to the observed, and the time‐dependent electron energy was obtained by using these parameters. The energy‐loss rates of hot electrons are at least twice smaller than the calculated ones induced by the electron‐polar phonon scattering, including the screening effect due to the high carrier density.
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Call Number Serial 635
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Author Burke, P. J.; Schoelkopf, R. J.; Prober, D. E.; Skalare, A.; Karasik, B. S.; Gaidis, M. C.; McGrath, W. R.; Bumble, B.; LeDuc, H. G.
Title Mixing and noise in diffusion and phonon cooled superconducting hot-electron bolometers Type Journal Article
Year 1999 Publication J. Appl. Phys. Abbreviated Journal
Volume 85 Issue 3 Pages (up) 1644-1653
Keywords HEB, mixer
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ISSN 0021-8979 ISBN Medium
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Notes Approved no
Call Number Serial 556
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