In situ boron-doped polycrystalline Si1-xGex (poly-Si1-xGex) films deposited by ultrahigh vacuum chemical vapor deposition (UHV/CVD) system were characterized. Optimum fitted values of grain boundary trap state densities, 4.0 × 1012 cm-2 and 4.9 × 1012 cm-2 were obtained for poly-Si and poly-Si0.79Ge0.21, respectively. The extracted average carrier concentration in the grain agrees with secondary ion mass spectroscopy (SIMS) analysis. In turn, we found that these films are suitable Hall elements to sense magnetic field. Experimental results show that the sensitivity decreased with the increasing input current, which can be well explained using the thermionic emission theory. Finally, we use these films to fabricate thin film transistors.