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Krause, S.; Mityashkin, V.; Antipov, S.; Gol’tsman, G.; Meledin, D.; Desmaris, V.; Belitsky, V.; Rudziński, M. |
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Reduction of phonon escape time for nbn hot electron bolometers by using gan buffer layers |
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Journal Article |
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2017 |
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IEEE Trans. Terahertz Sci. Technol. |
Abbreviated Journal |
IEEE Trans. Terahertz Sci. Technol. |
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7 |
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1 |
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53-59 |
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NbN HEB mixer |
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In this paper, we investigated the influence of the GaN buffer layer on the phonon escape time of phonon-cooled hot electron bolometers (HEBs) based on NbN material and compared our findings to conventionally employed Si substrate. The presented experimental setup and operation of the HEB close to the critical temperature of the NbN film allowed for the extraction of phonon escape time in a simplified manner. Two independent experiments were performed at GARD/Chalmers and MSPU on a similar experimental setup at frequencies of approximately 180 and 140 GHz, respectively, and have shown reproducible and consistent results. By fitting the normalized IF measurement data to the heat balance equations, the escape time as a fitting parameter has been deduced and amounts to 45 ps for the HEB based on Si substrate as in contrast to a significantly reduced escape time of 18 ps for the HEB utilizing the GaN buffer layer under the assumption that no additional electron diffusion has taken place. This study indicates a high phonon transmissivity of the NbN-to-GaN interface and a prospective increase of IF bandwidth for HEB made of NbN on GaN buffer layers, which is desirable for future THz HEB heterodyne receivers. |
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2156-3446 |
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1330 |
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Shurakov, A.; Tong, Cheuk-yu E.; Grimes, P.; Blundell, R.; Golt'sman, G. |
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Title |
A microwave reflection readout scheme for hot electron bolometric direct detector |
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Journal Article |
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Year |
2015 |
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IEEE Trans. THz Sci. Technol. |
Abbreviated Journal |
IEEE Trans. THz Sci. Technol. |
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5 |
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81-84 |
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HEB detectors |
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In this paper, we propose and present data from a fast THz detector based on the repurpose of hot electron bolometer mixers (HEB) fabricated from superconducting NbN thinfilm. This detector is essentially a traditional NbN bolometer element that operates under the influence of a microwave pump. The in-jected microwave power serves the dual purpose of enhancing the detector sensitivity and reading out the impedance changes of the device in response to incidentTHz radiation. We have measured an optical Noise Equivalent Power of 4 pW/ Hz for our detector at a bath temperature of 4.2 K. The measurement frequency was 0.83 THz and the modulation frequency was 1.48 kHz. The readout
scheme is versatile and facilitates both high-speed operation as well as multi-pixel applications. |
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RPLAB @ atomics90 @ |
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950 |
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Klapwijk, T. M.; Semenov, A. V. |
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Title |
Engineering physics of superconducting hot-electron bolometer mixers |
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Journal Article |
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2017 |
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IEEE Trans. THz Sci. Technol. |
Abbreviated Journal |
IEEE Trans. THz Sci. Technol. |
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7 |
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6 |
Pages |
627-648 |
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HEB mixers |
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Superconducting hot-electron bolometers are presently the best performing mixing devices for the frequency range beyond 1.2 THz, where good-quality superconductor-insulator-superconductor devices do not exist. Their physical appearance is very simple: an antenna consisting of a normal metal, sometimes a normal-metal-superconductor bilayer, connected to a thin film of a narrow short superconductor with a high resistivity in the normal state. The device is brought into an optimal operating regime by applying a dc current and a certain amount of local-oscillator power. Despite this technological simplicity, its operation has found to be controlled by many different aspects of superconductivity, all occurring simultaneously. A core ingredient is the understanding that there are two sources of resistance in a superconductor: a charge-conversion resistance occurring at a normal-metal-superconductor interface and a resistance due to time-dependent changes of the superconducting phase. The latter is responsible for the actual mixing process in a nonuniform superconducting environment set up by the bias conditions and the geometry. The present understanding indicates that further improvement needs to be found in the use of other materials with a faster energy relaxation rate. Meanwhile, several empirical parameters have become physically meaningful indicators of the devices, which will facilitate the technological developments. |
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2156-342X |
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1292 |
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Shurakov, A.; Seliverstov, S.; Kaurova, N.; Finkel, M.; Voronov, B.; Goltsman, G. |
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Title |
Input bandwidth of hot electron bolometer with spiral antenna |
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Journal Article |
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2012 |
Publication |
IEEE Trans. THz Sci. Technol. |
Abbreviated Journal |
IEEE Trans. THz Sci. Technol. |
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2 |
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4 |
Pages |
400-405 |
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NbN HEB bolometers bandwidth, log-spiral antenna |
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We report the results of our study of the input bandwidth of hot electron bolometers (HEB) embedded into the planar log-spiral antenna. The sensitive element is made of the ultrathin superconducting NbN film patterned as a bridge at the feed of the antenna. The contacts between the antenna and a sensitive element are made from in situ deposited gold (i.e., deposited over NbN film without breaking vacuum), which gives high quality contacts and makes the response of the HEB at higher frequencies less affected by the RF loss. An accurate experimental spectroscopic procedure is demonstrated that leads to the confirmation of the wide ( 8 THz) bandwidth in this antenna coupled device. |
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2156-342X |
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1161 |
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Finkel, M.; Thierschmann, H.; Galatro, L.; Katan, A. J.; Thoen, D. J.; de Visser, P. J.; Spirito, M.; Klapwijk, T. M. |
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Title |
Performance of THz components based on microstrip PECVD SiNx technology |
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Journal Article |
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Year |
2017 |
Publication |
IEEE Trans. THz Sci. Technol. |
Abbreviated Journal |
IEEE Trans. THz Sci. Technol. |
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Volume |
7 |
Issue |
6 |
Pages |
765-771 |
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Keywords |
transmission line measurements, power transmission lines, dielectrics, couplers, submillimeter wave circuits, coplanar waveguides, micromechanical devices |
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We present a performance analysis of passive THz components based on Microstrip transmission lines with a 2-μmthin plasma-enhanced chemical vapor deposition grown silicon nitride (PECVD SiNX) dielectric layer. A set of thru-reflect-line calibration structures is used for basic transmission line characterizations. We obtain losses of 9 dB/mm at 300 GHz. Branchline hybrid couplers are realized that exhibit 2.5-dB insertion loss, 1-dB amplitude imbalance, and -26-dB isolation, in agreement with simulations. We use the measured center frequency to determine the dielectric constant of the PECVD SiN x , which yields 5.9. We estimate the wafer-to-wafer variations to be of the order of 1%. Directional couplers are presented which exhibit -12-dB transmission to the coupled port and -26 dB to the isolated port. For transmission lines with 5-μm-thin silicon nitride (SiN x ), we observe losses below 4 dB/mm. The thin SiN x dielectric membrane makes the THz components compatible with scanning probe microscopy cantilevers allowing the application of this technology in on-chip circuits of a THz near-field microscope. |
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