Fabrication and Characterization of Ultrathin PBCO/YBCO/PBCO Constrictions for Hot Electron Bolometer THz Mixing Application

Superconducting Hot Electron Bolometer (HEB) mixers are a competitive alternative to conventional mixer technologies in the terahertz range because of their ultrawide bandwidth, high conversion gain, and low intrinsic noise level, even at 77 K. A technological process to realize HEBs based on high-Tc YBa₂Cu₃O_7-delta (YBCO) materials is described. Ultra- thin 12 to 40 nm layers were sputtered on MgO (100) substrates, sub-micrometer constrictions (0.5 mum times 0.5 mum) were etched on these and log-periodic gold antennas were then integrated. Good superconducting properties were measured after the whole process. Electrical transport characteristics of the device are discussed, ageing effects are considered and regular bolometric THz response results are given.