Microbolometers Based on Amorphous Silicon–Germanium Films With Embedded Nanocrystals

In this paper, we have fabricated and characterized uncooled microbolometers using as infrared element intrinsic amorphous silicon-germanium films with embedded nanocrystals with a dimension in the range of ~2-4 nm. The presence of nanocrystals in the amorphous films reduces the density of defects, improves the transport properties, and specially improves the films stability against radiation. On the other hand, the combination of silicon and germanium in one alloy allows to improve the film conductivity and the temperature coefficient of resistance (TCR), without the necessity of perform doping. Large values of TCR have been demonstrated in the microbolometers, as large as -6.6% K^-1, which in fact is the largest value reported for this kind of devices, and consequently large detectivity values were obtained in the reported devices (2 × 10⁹ cmHz^1/2W^-1).