Design analysis of a novel hot-electron microbolometer

The authors propose a novel antenna coupled microbolometer which makes use of the weak coupling between electrons and phonons in a metal at low temperatures. The radiation is collected by a planar lithographed antenna and thermalized in a thin metal strip. The resulting temperature rise of the electrons is detected by a tunnel junction, where part of the metal strip forms the normal electrode. The active area of the bolometer is thermally coupled by its small volume, by the thermal resistance between the electrons and phonons in the strip, and by the reflection of quasi-particles at the interface between the strip and the superconducting antenna. Design calculations based on a metal volume of 2 mu m*6 mu m*0.05 mu m at an operating temperature of 100 mK give an NEP of about 3*10/sup -19/ WHz/sup -1/2/, a time constant of about 10 mu s, and a responsivity of about 10/sup 9/ V/W. The calculated sensitivity is almost two orders of magnitude higher than that of the best available direct detectors of millimeter and submillimeter radiation operated at the same temperature.<>