We have performed epitaxial growth of Ge films on (NH4)(2)S-treated GaAs (0 0 1) substrates under various growth temperatures using molecular. bt am epitaxy. We confirmed that this sulfur passivation is quite effective for preventing the oxidation of GaAy sulface. Thus, the Ge films were grown epitaxially on GaAs substrate without thermal cleaning. The electric properties of Ge films were investigated using Hall measurement and it was found that the conduction type of Ge films can be controlled by growth temperature. The Ga-S bond is thought to be the key for conduction typo control, although the details are not identified yet.