Epitaxial GaAs layers have been grown on Ge-coated Si substrates. Deposition of epitaxial Ge was performed by electron beam evaporation onto a <100> Si substrate. GaAs was then deposited by organometallic vapor-phase epitaxy. Films grown over large areas (∼1 cm2) and by selective epitaxy in stripe patterns (∼50 μm wide) have been evaluated by a number of techniques to determine structural and electrical properties. In addition, we report what we believe to be the first LEDs fabricated in GaAs/Ge/Si heterostructures.