Bandurin, D. A., Gayduchenko, I., Cao, Y., Moskotin, M., Principi, A., Grigorieva, I. V., et al. (2018). Dual origin of room temperature sub-terahertz photoresponse in graphene field effect transistors. Appl. Phys. Lett., 112(14), 141101 (1 to 5).
Abstract: Graphene is considered as a promising platform for detectors of high-frequency radiation up to the terahertz (THz) range due to its superior electron mobility. Previously, it has been shown that graphene field effect transistors (FETs) exhibit room temperature broadband photoresponse to incoming THz radiation, thanks to the thermoelectric and/or plasma wave rectification. Both effects exhibit similar functional dependences on the gate voltage, and therefore, it was difficult to disentangle these contributions in previous studies. In this letter, we report on combined experimental and theoretical studies of sub-THz response in graphene field-effect transistors analyzed at different temperatures. This temperature-dependent study allowed us to reveal the role of the photo-thermoelectric effect, p-n junction rectification, and plasmonic rectification in the sub-THz photoresponse of graphene FETs.
D.A.B. acknowledges the Leverhulme Trust for financial support. The work of D.S. was supported by Grant No. 16-19-10557 of the Russian Scientific Foundation (theoretical model). G.F., I.G., M.M., and G.G. acknowledge the Russian Science Foundation [Grant No. 14-19-01308 (MIET, cryostat upgrade) and Grant No. 17-72-30036, (MSPU, photoresponse measurements), the Ministry of Education and Science of the Russian Federation (Contract No. 14.B25.31.0007 (device fabrication) and Task No. 3.7328.2017/LS (NEP analyses)] and the Russian Foundation for Basic Research [Grant No. 15-02-07841 (device design)]. The authors are grateful to Professor M. S. Shur for helpful discussions.
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Baselmans, J. J. A., Baryshev, A., Reker, S. F., Hajenius, M., Gao, J. R., Klapwijk, T. M., et al. (2005). Direct detection effect in small volume hot electron bolometer mixers. Appl. Phys. Lett., 86(16), 163503 (1 to 3).
Abstract: We measure the direct detection effect in a small volume (0.15μm×1μm×3.5nm)(0.15μm×1μm×3.5nm) quasioptical NbN phonon cooled hot electronbolometermixer at 1.6THz1.6THz. We find that the small signal sensitivity of the receiver is underestimated by 35% due to the direct detection effect and that the optimal operating point is shifted to higher bias voltages when using calibration loads of 300K300K and 77K77K. Using a 200GHz200GHzbandpass filter at 4.2K4.2K the direct detection effect virtually disappears. This has important implications for the calibration procedure of these receivers in real telescope systems.
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Baselmans, J. J. A., Hajenius, M., Gao, J. R., Klapwijk, T. M., de Korte, P. A. J., Voronov, B., et al. (2004). Doubling of sensitivity and bandwidth in phonon cooled hot electron bolometer mixers. Appl. Phys. Lett., 84(11), 1958–1960.
Abstract: We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. We show experimentally that both the receiver noise temperature and the gain bandwidth can be improved by more than a factor of 2 by cleaning the interface and adding an additional superconducting interlayer to the contact pad. Using this we obtain a double sideband receiver noise temperature TN,DSB=950 K
at 2.5 THz and 4.3 K, uncorrected for losses in the optics. At the same bias point, we obtain an IF gain bandwidth of 6 GHz.
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Bennett, D. A., Schmidt, D. R., Swetz, D. S., & Ullom, J. N. (2014). Phase-slip lines as a resistance mechanism in transition-edge sensors. Appl. Phys. Lett., 104, 042602.
Abstract: The fundamental mechanism of resistance in voltage-biased superconducting films is poorly understood despite its importance as the basis of transition-edge sensors (TESs). TESs are utilized in state-of-the-art microbolometers and microcalorimeters covering a wide range of energies and applications. We present a model for the resistance of a TES based on phase-slip lines (PSLs) and compare the model to data. One of the model's predictions, discrete changes in the number of PSLs, is a possible explanation for the observed switching between discrete current states in localized regions of bias.
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Bueno, J., Coumou, P. C. J. J., Zheng, G., de Visser, P. J., Klapwijk, T. M., Driessen, E. F. C., et al. (2014). Anomalous response of superconducting titanium nitride resonators to terahertz radiation. Appl. Phys. Lett., 105, 192601 (1 to 5).
Abstract: We present an experimental study of kinetic inductance detectors (KIDs) fabricated of atomic layer deposited TiN films and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with the increase in radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride/aluminium (NbTiN/Al) and all-aluminium (all-Al) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations.
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