Balanced superconductor–insulator–superconductor mixer on a 9 µm silicon membrane

We present a 380?520?GHz balanced superconductor?insulator?superconductor (SIS) mixer on a single silicon substrate. All radio-frequency (RF) circuit components are fabricated on a 9??m thick membrane. The intermediate frequency (IF) is separately amplified and combined. The balanced mixer chip, using Nb/Al/Al2O3/Nb SIS junctions, is mounted in a tellurium copper waveguide block at 4.2?K using Au beam lead contacts. We find uncorrected minimum receiver double-sideband noise temperatures of 70?K and a noise suppression of up to 18?dB, measured within a 440?495?GHz RF and a 4?8?GHz IF bandwidth, representing state-of-the-art device performance.