DESIGN ANALYSIS OF A NOVEL HOT-ELECTRON MICROBOLOMETER

We 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. All components are deposited directly on a substrate so that arrays can be conveniently produced by conventional lithographic techniques. The active area of the bolometer is thermally decoupled by its small volume, by the thermal resistance between the electrons and phonons in the strip, and by the reflection of quasiparticles at the interface between the strip and the superconducting antenna. Design calculations based on a metal volume of 2x6x0.05 mu m(3) at an operating temperature of T= 100 mK give an NEP approximate to 3x10(-19) WHZ(-1/2) time constant approximate to 10 mu s, and responsivity approximate to 10(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.