Uncooled micro-bolometer based on amorphous germanium film

The fabrication and characterization of an uncooled micro-bolometer, in which the sensing material is amorphous germanium (a-Ge:F) is presented. In order to obtain thermal isolation, the micro-bolometer was fabricated on a silicon dioxide membrane, which was made on a silicon wafer by micro-machining techniques. The sensing layer was deposited from GeF4 + H2 mixture by low frequency plasma-enhanced chemical vapor deposition. The a-Ge:F film had high thermal coefficient of resistance at room temperature α=0.04 and moderate conductivity σRT=2.5×10−3 Ω−1 cm−1. The micro-bolometer was characterized by the measurements of current–voltage characteristics in dark and under infrared illumination with a black body at temperature Tbb=1123 K. Thermal and noise characteristics were also measured. The micro-bolometer having the pixel area Ad=60×60 μm2 demonstrated thermal resistance Rth=5×106 K W−1, current responsivity RI=6.2 mA W−1, voltage responsivity RV=4.2×106 V W−1 and detectivity D∗=8×106 cm W Hz1/2.