IF impedance and mixer gain of NbN hot electron bolometers

J. W. Kooi, J. J. A. Baselmans, M. Hajenius, J. R. Gao, T. M. Klapwijk, P. Dieleman, A. Baryshev, G. de Lange

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The intermediate frequency (IF) characteristics, the frequency dependent IF impedance, and the mixer conversion gain of a small area hot electron bolometer (HEB) have been measured and modeled. The device used is a twin slot antenna coupled NbN HEB mixer with a bridge area of 1×0.15μm2, and a critical temperature of 8.3K. In the experiment the local oscillator frequency was 1.300THz, and the (IF) 0.05-10GHz. We find that the measured data can be described in a self-consistent manner with a thin film model presented by Nebosis et al. [Proceedings of the Seventh International Symposium on Space Terahertz Technology, Charlottesville, VA, 1996 (unpublished), pp. 601-613], that is based on the two temperature electron-phonon heat balance equations of Perrin-Vanneste [J. Phys. (Paris) 48, 1311 (1987)]. From these results the thermal time constant, governing the gain bandwidth of HEB mixers, is observed to be a function of the electron-phonon scattering time, phonon escape time, and the electron temperature. From the developed theory the maximum predicted gain bandwidth for a NbN HEB is found to be 5.5-6GHz. In contrast, the gain bandwidth of the device under discussion was measured to be ˜2.3GHz which, consistent with the outlined theory, is attributed to a somewhat low critical temperature and nonoptimal film thickness (6nm).
Original languageEnglish
Article number044511
Pages (from-to)044511-1 - 044511-8
Number of pages8
JournalJournal of Applied Physics
Issue number4
Publication statusPublished - 1-Feb-2007


  • Modulators and demodulators
  • discriminators comparators mixers limiters and compressors
  • Photodetectors
  • Superconducting infrared submillimeter and millimeter wave detectors

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