Very High Current Nb/A1N/Nb Tunnel Junctions for Low-noise Submillimeter Mixers
Very High Current Nb/A1N/Nb Tunnel Junctions for Low-noise Submillimeter Mixers
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通讯作者：
J. Zmuidzinas;B. Bumble
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作者：
J. Zmuidzinas;B. Bumble
我们用极高电流密度的Nb/AlN/Nb隧道结(JC_30kA·cm~(-2))制作并测试了亚毫米波超导体-绝缘体-超导体(SIS)混合器。这些结具有低的电阻面积积(RNA5.6f2#m2)，良好的亚隙与正常电阻比Rsg/Rn10，以及良好的Run-to-Run重复性。从傅里叶变换光谱仪测量，我们推断wRNC-1在270 GHz。这比通常适用于低噪声混频器的Nb/AlOx/Nb结的性能提高了2.5倍。AlN势垒结确实能够进行低噪声操作：对于未经优化的器件，我们测量了未校正的接收器噪声温度为533 GHz的TRX-110K(DSB)。除了在较低频率下提供更宽的带宽操作外，AlN势垒结还将通过减少调谐电路中的射频损耗来显著提高THzSIS混频器的性能。
We have fabricated and tested submillimeter-wave superconductor-insulator_superconductor (SIS) mixers using very high current density Nb/A1N/Nb tunnel junctions (Jc _ 30 kA cm-2). The junctions have low resistance-area products (RNA ,._ 5.6 f2#m2), good subgap to normal resistance ratios Rsg/RN _ 10, and good run-to-run reproducibility. From Fourier transform spectrometer measurements, we infer that wRNC --- 1 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 receiver noise temperature of TRx ----ll0K (DSB) 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.