The effects of In doping on crystalline qualities are demonstrated in the heteroepitaxy of GaAs on Si grown by molecular beam epitaxy. The etch pit density of the GaAs layers doped with In at 8×1017cm−3decreased by a factor of 7 compared with undoped GaAs layers. Dark regions observed in electron beam induced current images became small by In doping. The improvement of the crystalline qualities was also verified by Raman spectroscopy.