DIFFUSION COOLING MECHANISM IN A HOT-ELECTRON NBC MICROBOLOMETER MIXER

The crossover between the electron-phonon relaxation and the diffusion transport of hot electrons in an NbC microbolometer has been studied. At least an 80 ps relaxation time can be achieved in 0.2 mu m long br idges of the material with a diffusivity of 8 cm(2)/s. The high diffus ivity is accompanied by a large sheet resistance (approximate to 10 Om ega) that simplifies the match of the mixer device made of NbC to plan ar antenna at terahertz frequencies. The intrinsic noise mechanisms im ply a very low mixer noise temperature of the order of a few tens of K elvin, independent on the radiation frequency. (C) 1996 American Insti tute of Physics.