Photoresponse above 85 K of selective epitaxy grown high-T_csuperconducting microwires

Superconducting single-photon detectors have become a very promising infrared photon counting technology. Utilizing high-Tc superconductors to implement photon counters is significantly more practical due to their much higher operating temperatures. We report photoresponse above 85 K of YB a 2 C u 3 O 7 - δ (YBCO) microwires fabricated using selective epitaxial growth (SEG), demonstrating their high photon detection efficiency. SEG does not require post-deposition treatment of the YBCO layer, thus avoiding material damage and degradation, typically occurring in conventional submicrometer YBCO device fabrication. Our results show excellent superconducting performance with a Tc of up to 89 K and a sharp transition width of Δ T ∼ 2 K, as well as a relatively high critical current density Jc of ∼ 5.7 × 10 5 A / c m 2 at 77 K. The optical response of our YBCO microwires, especially the high responsivity of ∼ 3 × 10 3 mV / (nW / u m 2), paves the way for infrared single-photon detection using high-Tc superconductors.