| Records |
| Author |
Krause, S.; Mityashkin, V.; Antipov, S.; Gol’tsman, G.; Meledin, D.; Desmaris, V.; Belitsky, V.; Rudziński, M. |
| Title |
Reduction of phonon escape time for nbn hot electron bolometers by using gan buffer layers |
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Journal Article |
| Year |
2017 |
Publication |
IEEE Trans. Terahertz Sci. Technol. |
Abbreviated Journal |
IEEE Trans. Terahertz Sci. Technol. |
| Volume |
7 |
Issue |
1 |
Pages  |
53-59 |
| Keywords |
NbN HEB mixer |
| Abstract |
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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Krause, S.; Mityashkin, V.; Antipov, S.; Gol'tsman, G.; Meledin, D.; Desmaris, V.; Belitsky, V.; Rudzinski, M. |
| Title |
Study of IF bandwidth of NbN hot electron bolometers on GaN buffer layer using a direct measurement method |
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Conference Article |
| Year |
2016 |
Publication |
Proc. 27th Int. Symp. Space Terahertz Technol. |
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30-32 |
| Keywords |
NbN HEB, GaN buffer layer |
| Abstract |
In this paper, we present a reliable measurement method to study the influence of the GaN buffer layer on phonon-escape time in comparison with commonly used Si substrates and, in consequence, on the IF bandwidth of HEBs. One of the key aspects is to operate the HEB mixer at elevated bath temperatures close to the critical temperature of the NbN ultra-thin film, where contributions from electron-phonon processes and self-heating effects are relatively small, therefore IF roll-off will be governed by the phonon-escape.Two independent experiments were performed at GARD and MSPU on a similar experimental setup at frequencies of approximately 180 and 140 GHz, respectively, and have shown reproducible and consistent results. The entire IF chain was characterized by S-parameter measurements. We compared the measurement results of epitaxial NbN grown onto GaN buffer-layer with Tc of 12.5 K (4.5nm) with high quality polycrystalline NbN films on Si substrate with Tc of 10.5K (5nm) and observed a strong indication of an enhancement of phonon escape to the substrate by a factor of two for the NbN/GaN material combination. |
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1202 |
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Meledin, D.; Pantaleev, M.; Pavolotsky, A.; Risacher, C.; Belitsky, V.; Drakinskiy, V.; Cherednichenko, S. |
| Title |
Balanced waveguide HEB mixer for APEX 1.3 THz receiver |
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Conference Article |
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2005 |
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Proc. 16th Int. Symp. Space Terahertz Technol. |
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Göteborg, Sweden |
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RPLAB @ s @ wg_balanced |
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362 |
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Belitsky, V.; Desmaris, V.; Dochev, D.; Meledin, D.; Pavolotsky, A. |
| Title |
Towards Multi-Pixel Heterodyne Terahertz Receivers |
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Conference Article |
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2011 |
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Proc. 22th Int. Symp. Space Terahertz Technol. |
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Terahertz multi-pixel heterodyne receivers introduce multiple challenges for their implementation, mostly due to the extremely small dimensions of all components and even smaller tolerances in terms of alignment, linear dimensions and waveguide component surface quality. In this manuscript, we present a concept of terahertz multi-pixel heterodyne receiver employing optical layout using polarization split between the LO and RF. The frontend isbased on a waveguide balanced HEB mixer for the frequency band 1.6 – 2.0 THz. The balanced HEB mixer followsthe layout of earlier demonstrated APEX T2 mixer. However for the mixer presented here, we implemented split-block layout offering inimized lengths of all waveguides and thus reducing the associated RF loss. The micromachining methods employed for producing the mixer housing and the HEB mixer chip are very suitable for producing multiple structures and hence are in-line with requirements of multi-pixel receiver technology. The demonstrated relatively simple mounting of the mixer chip with self-aligning should greatly facilitate the integration of such multi-channel receiver. Index Terms—Instrumentation, Multi-pixel, Terahertz, Waveguide Balanced Mixer. |
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RPLAB @ atomics90 @ |
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