Fabrication of GaAs/Si heterostructures and their photoelectric properties are investigated by Raman, photoluminescence and Hall-effect measurements. The crystallinity of GaAs epilayers grown on Si substrate is significantly affected by the substrate orientation and the growth method. The photoelectric properties of GaAs epilayers grown on Si (211) substrates deposited by using a two-step growth method are improved. These results indicate that GaAs epilayers grown on Si (100) and Si (211) substrates by using two-step growth method are promising for potential applications in high-speed and high-frequency photoelectric devices. The crystallinity of GaAs epilayers grown on Si substrates is significantly affected by the substrate orientation and the growth method. These results indicate that GaAs epilayers grown on Si (100) and Si (211) substrates by using two-step growth methods are promising for potential applications in high -speed and high-frequency photoelectric devices.