ELECTRICAL RESPONSE OF BA1-XKXBIO3 POLYCRYSTALLINE THIN-FILMS TO INFRARED RADIATION

The electrical response to infrared radiation of polycrystalline Ba 1-xKxBiO3 thin films on MgO(100) and sapphire substrates with Tc's of approximately 20 K is studied using modulated laser light at a wavelength of 1.3 μm. These films clearly show nonbolometric responses which are quite similar to those observed in BaPb 1-xBixO3 optical detectors based on nonequilibrium superconductivity. The responsivity values at about 15 K are one or two orders of magnitude larger than those for the copper-oxide-based high Tc superconductors with much larger electronic density of states at the Fermi level. These results indicate that Ba1-xM xBiO3(M=K,Rb) is a promising candidate for a sensitive nonequilibrium infrared detector which can be operated using a closed-cycle refrigerator.