An uncooled microbolometer infrared detector based on polycrystalline silicon germanium thin film

This paper reports an uncooled microbolometer infrared detector with polycrystalline silicon-germanium (poly-Si0.7Ge0.3) thermistor as the active element. Using the anisotropic etching technique, the poly-Si0.7Ge0.3 thermistor is formed on a two legs supported microbridge suspended on a silicon substrate to decrease the thermal conductance. The dependences of the resistance and the temperature coefficient of resistance on temperature are described. The characteristics of the detector are investigated to infrared radiation in the spectral region of 8-14 mum at an operation temperature of 296K. Measurements and calculations show that at a chopper frequency of 30Hz, the detector provides a peak responsivity of 30,000V/W, a peak detectivity of 1.68-10(9) cmHz(1/2)/W and a thermal response time of 13.2 ms.