We report the study of a fabrication process and characterization of un-cooled micro-bolometers based on silicon germanium thin films deposited by low frequency PE CVD technique at low temperature and fully compatible with the IC fabrication technology. Surface micromachining techniques were used for the micro-bolometer fabrication onto a silicon wafer. The a-SixGe1-x:H thermo-sensing film used in those devices have shown high activation energy providing high thermal coefficient of resistance and improved but still high resistance. We studied the effect on the electrical properties of the device when boron is incorporated in the a-SixGe1-x:H film. The temperature dependence of conductivity ¾(T), current-voltage characteristics I(U) and noise spectral density have been measured in order to characterize and compare the performance of micro-bolometers with both types of films: a-SixGe1-x:H and a-GexBySiz:H.