Deposition of silicon-germanium (Si1-xGex) thin films in a hot wall tubular low-pressure chemical vapor deposition (LPCVD) furnace using SiH4 and GeH4 at 100 mTorr with temperatures ranging from 297 to 650 degrees C has been studied. The deposited films range from pure Si to pure Ge. The deposition rate behavior is presented. The apparent activation energy of deposition rate of Ge from GeH4 in reaction-rate limited regime was found to be 0.91 eV, and for the deposition of Si from SiH4 was found to be 1.7 eV. The relation between the GeH4 mole fraction in the gas phase during deposition and Ge atomic fraction in the film is described. A model based on the sticking probability of Si and Ge precursors on the surface is proposed to describe this relation.