Very high-current-density NbÕAlNÕNb tunnel junctions for low-noise submillimeter mixers
نویسندگان
چکیده
We have fabricated and tested submillimeter-wave superconductor–insulator–superconductor ~SIS! mixers using very high-current-density Nb/AlN/Nb tunnel junctions (Jc'30 kA cm ). The junctions have low-resistance-area products (RNA'5.6 V mm ), good subgap-to-normal resistance ratios Rsg /RN'10, and good run-to-run reproducibility. From Fourier transform spectrometer measurements, we infer that vRNC51 at 270 GHz. This is a factor of 2.5 improvement over what is generally available with Nb/AlOx/Nb junctions suitable for low-noise mixers. The AlN-barrier junctions are indeed capable of low-noise operation: we measure an uncorrected double-sideband receiver noise temperature of TRX5110 K at 533 GHz for an unoptimized device. In addition to providing wider bandwidth operation at lower frequencies, the AlN-barrier junctions will considerably improve the performance of THz SIS mixers by reducing rf loss in the tuning circuits. © 2000 American Institute of Physics. @S0003-6951~00!04915-9#
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