We have investigated the deposition behavior of Si1-xGex(x less than or equal to 0.31) films using Si2H6 and GeH4 source gases in low pressure chemical vapor deposition. The deposition temperature and pressure were varied from 400 to 500 degrees C and from 0.5 to 1 Torr, respectively. We identified that the germanium content in the film slightly increased with pressure, while it did not change with temperature at a fixed flow rate of two source gases. The deposition rate was enhanced as the germanium incorporation in the film was increased, and the activation energy obtained from the Arrhenius plot of deposition rate decreased from 1.5 eV for Si to 1 eV for Si0.69Ge0.31. Both these results were attributed to lowering the activation energy of hydrogen desorption from the growing film surface. The transition temperature from amorphous to polycrystalline during the deposition was about 475 degrees C for the Si0.69Ge0.31 alloy film, and the average grain size of this film deposited at 500 degrees C was measured as approximately 60 nm.