Comparison of three un-cooled micro-bolometers configurations based on amorphous silicon–germanium thin films deposited by plasma

Abstract We present a comparative study of three configurations of un-cooled micro-bolometers based on amorphous silicon–germanium thin films deposited by plasma at low temperature and compatible with the IC technology. The temperature dependence of conductivity σ ( T ), current–voltage characteristics I ( U ) and current noise spectral density (NSD) have been measured in order to characterize and compare the performance characteristics, such as responsivity and detectivity in three configurations of micro-bolometers: (a) planar structure with a silicon–germanium intrinsic (a-Si x Ge y :H) thermo-sensing film; (b) planar structure with a silicon–germanium–boron alloy (a-Si x Ge y B z :H) thermo-sensing film and (c) sandwich structure with an intrinsic (a-Si x Ge y :H) thermo-sensing film. The samples studied demonstrated different cell resistance R c = 10 5 –10 8 Ω and responsivities R I = 10 1 –10 −3 A/W, while the values of detectivity D ∗ were quite similar D ∗ = (4–7) × 10 9 cm Hz 1/2 W −1 .