Uncooled micro-bolometer based on amorphous germanium film

Abstract

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 GeF 4 + H 2 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 σ RT=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 T bb=1123 K. Thermal and noise characteristics were also measured. The micro-bolometer having the pixel area A d=60×60 μm 2 demonstrated thermal resistance R th=5×10 6 K W −1, current responsivity R I =6.2 mA W −1, voltage responsivity R V =4.2×10 6 V W −1 and detectivity D ∗=8×10 6 cm W Hz 1/2.