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Hübers, H. - W., Semenov, A., Richter, H., Birk, M., Krocka, M., Mair, U., et al. (2002). Terahertz Heterodyn Receiver with a hot-electron bolometer mixer. In U. Wolf, J. Farhoomand, & C. R. McCreight (Eds.), Far-IR, Sub-mm & MM Detector Technology Workshop (pp. 3–24). NASA CP. NASA.
Abstract: During the past decade major advances have been made regarding low noise mixers for terahertz (THz) heterodyne receivers. State of the art hot-electron-bolometer (HEB) mixers have noise temperatures close to the quantum limit and require less than a µW power from the local oscillator (LO). The technology is now at a point where the performance of a practical receiver employing such mixer, rather than the figures of merit of the mixer itself, are of major concern. We have incorporated a phonon-cooled NbN HEB mixer in a 2.5 THz heterodyne receiver and investigated the performance of the receiver. This yields important information for the development of heterodyne receivers such as GREAT (German receiver for astronomy at THz frequencies aboard SOFIA) [1] and TELIS (Terahertz limb sounder), a balloon borne heterodyne receiver for atmospheric research [2]. Both are currently under development at DLR.
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Hübers, H. - W., Semenov, A., Richter, H., Birk, M., Krocka, M., Mair, U., et al. (2002). Terahertz heterodyne receiver with a hot-electron bolometer mixer. In J. Wold, & J. Davidson (Eds.), Proc. Far-IR, Sub-mm, and mm Detector Technology Workshop.
Abstract: During the past decade major advances have been made regarding low noise mixers for terahertz (THz) heterodyne receivers. State of the art hot-electron-bolometer (HEB) mixers have noise temperatures close to the quantum limit and require less than a µW power from the local oscillator (LO). The technology is now at a point where the performance of a practical receiver employing such mixer, rather than the figures of merit of the mixer itself, are of major concern. We have incorporated a phonon-cooled NbN HEB mixer in a 2.5 THz heterodyne receiver and investigated the performance of the receiver. This yields important information for the development of heterodyne receivers such as GREAT (German receiver for astronomy at THz frequencies aboard SOFIA)[1] and TELIS (Terahertz limb sounder), a balloon borne heterodyne receiver for atmospheric research [2]. Both are currently under development at DLR.
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Yagubov, P., Gol'tsman, G., Voronov, B., Seidman, L., Siomash, V., Cherednichenko, S., et al. (1996). The bandwidth of HEB mixers employing ultrathin NbN films on sapphire substrate. In Proc. 7th Int. Symp. Space Terahertz Technol. (pp. 290–302). Charlottesville, Virginia, USA.
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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Vakhtomin, Y. B., Finkel, M. I., Antipov, S. V., Smirnov, K. V., Kaurova, N. S., Drakinskii, V. N., et al. (2003). The gain bandwidth of mixers based on the electron heating effect in an ultrathin NbN film on a Si substrate with a buffer MgO layer. J. of communications technol. & electronics, 48(6), 671–675.
Abstract: Measurements of the intermediate frequency band 900 GHz of mixers based on the electron heating effect (EHE) in 2-nm- and 3.5-nm-thick superconducting NbN films sputtered on MgO and Si substrates with buffer MgO layers are presented. A 2-nm-thick superconducting NbN film with a critical temperature of 9.2 K has been obtained for the first time using a buffer MgO layer.
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Tret'yakov, I. V., Kaurova, N. S., Voronov, B. M., Anfert'ev, V. A., Revin, L. S., Vaks, V. L., et al. (2016). The influence of the diffusion cooling on the noise band of the superconductor NbN hot-electron bolometer operating in the terahertz range. Tech. Phys. Lett., 42(6), 563–566.
Abstract: Results of an experimental study of the noise temperature (Tn) and noise bandwidth (NBW) of the superconductor NbN hot-electron bolometer (HEB) mixer as a function of its temperature (Tb) are presented. It was determined that the NBW of the mixer is significantly wider at temperatures close to the critical ones (Tc) than are values measured at 4.2 K. The NBW of the mixer measured at the heterodyne frequency of 2.5 THz at temperature Tb close to Tc was ~13 GHz, as compared with 6 GHz at Tb = 4.2 K. This experiment clearly demonstrates the limitation of the thermal flow from the NbN bridge at Tb â‰<aa> Tc for mixers manufactured by the in situ technique. This limitation is close in its nature to the Andreev reflection on the superconductor/ metal boundary. In this case, the noise temperature of the studied mixer increased from 1100 to 3800 K.
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Meledin, D., Tong, C. Y. - E., Blundell, R., Kaurova, N., Smirnov, K., Voronov, B., et al. (2002). The sensitivity and IF bandwidth of waveguide NbN hot electron bolometer mixers on MgO buffer layers over crystalline quartz. In Harvard university (Ed.), Proc. 13th Int. Symp. Space Terahertz Technol. (pp. 65–72). Cambridge, MA, USA.
Abstract: We have developed and characterized waveguide phonon-cooled NbN Hot Electron Bolometer (FMB) mixers fabricated from a 3-4 nm thick NbN film deposited on a 200nm thick MgO buffer layer over crystalline quartz. Double side band receiver noise temperatures of 900-1050 K at 1.035 THz, and 1300-1400 K at 1.26 THz have been measured at an intermediate frequency of 1.5 GHz. The intermediate frequency bandwidth, measured at 0.8 THz LO frequency, is 3.2 GHz at the optimal bias point for low noise receiver operation.
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Il'in, K., Siegel, M., Semenov, A., Engel, A., Hübers, H. - W., Hollmann, E., et al. (2004). Thickness dependence of superconducting properties of ultrathin Nb and NbN films. In AKF-Frühjahrstagung.
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Shurakov, A., Mikhalev, P., Mikhailov, D., Mityashkin, V., Tretyakov, I., Kardakova, A., et al. (2018). Ti/Au/n-GaAs planar Schottky diode with a moderately Si-doped matching sublayer. Microelectronic Engineering, 195, 26–31.
Abstract: In this paper, we report on the results of the study of the Ti/Au/n-GaAs planar Schottky diodes (PSD) intended for the wideband detection of terahertz radiation. The two types of the PSD devices were compared having either the dual n/n+ silicon dopant profile or the triple one with a moderately doped matching sublayer inserted. All the diodes demonstrated no noticeable temperature dependence of ideality factors and barrier heights, whose values covered the ranges of 1.15–1.50 and 0.75–0.85 eV, respectively. We observed the lowering of the flat band barrier height of ∼80 meV after introducing the matching sublayer into the GaAs sandwich. For both the devices types, the series resistance value as low as 20 Ω was obtained. To extract the total parasitic capacitance, we performed the Y-parameters analysis within the electromagnetic modeling of the PSD's behavior via the finite-element method. The capacitance values of 12–12.2 fF were obtained and further verified by measuring the diodes' response voltages in the frequency range of 400–480 GHz. We also calculated the AC current density distribution within the layered structures similar to those being experimentally studied. It was demonstrated that insertion of the moderately Si-doped matching sublayer might be beneficial for implementation of a PSD intended for the operation within the ‘super-THz’ frequency range.
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Averkin, A. S., Shishkin, A. G., Chichkov, V. I., Voronov, B. M., Goltsman, G. N., Karpov, A., et al. (2014). Tunable frequency-selective surface based on superconducting split-ring resonators. In 8th Metamaterials.
Abstract: We study a possibility to use the 2D superconducting metamaterial as a tunable frequency-selective surface (FSS). The proposed FSS is made of sub-wavelength size (l/14) metamaterial unit cells, where a split-ring resonator is embedded in a small iris aperture in a metal plane. The split-ring resonator is made of NbN film, and its resonance frequency is tuned by the temperature of the sample, changing the kinetic inductance of NbN film. The Ansoft HFSS simulation predicts the FSS tuning range of about 10-20 %. The developed superconducting FSS may be used as a tunable band-pass filter or modulator.
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Gao, J. R., Hajenius, M., Baselmans, J. J. A., Yang, Z. Q., Baryshev, A. M., Barends, R., et al. (2005). Twin-slot antenna coupled NbN hot electron bolometer mixers for space applications. In Proc. 9-th WMSCI (Vol. 9, pp. 148–153). International Institute of Informatics and Systemics.
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