Cryogenic amplifier with low input-referred voltage noise calibrated by shot noise measurement*

Project supported by the National Natural Science Foundation of China (Grant No. 11474008), the National Key Research and Development Program of China (Grant No. 2016YFA0300904), and the National Basic Research Program of China (Grant No. 2011CBA00106).
Yang Wuhao †, Wei Jian
       

(color online) Fabrication of Al/AlOx/Al tunneling junction. (a) SEM image of the shadow mask taken after the deposition of Aluminum films and before lift-off. The bilayer shadow mask consists of a top 200-nm thick polymethyl methacrylate (950 A4 PMMA) layer, used as a high-resolution electron resist, and a bottom 400-nm thick layer of polymer polydimethylglutarimide (PMGI SF6). A deep undercut in the bottom layer allows for overlapping of the films deposited at different incident angles. (b) Cross-section along the dashed line in panel (a). The first layer Al is deposited along the direction normal to the plane of the substrate, the second layer Al is deposited at a 30° incidence angle and parallel slit in panel (a). (c) SEM image of Al/AlOx/Al tunneling junction with dimensions 180 nm×1000 nm×70 nm. The 1st layer Al and the 2nd layer Al overlap on the different Ti/Au pattern leads, which we fabricated by UV lithography.