The effects of In-doping (0.04-0.59%) at low temperature on crystalline qualities are demonstrated in the heteroepitaxy of GaAs on Si grown by chemical beam epitaxy (CBE). From 4.2K photoluminescence it is clear that for an indium content of 0.04 and 0.29%, the intensity of the acceptor bound excitonic recombination at 1.492 eV has increased 2-fold and 4.5-fold, respectively. For the sample doped with 0.29% indium, the peak originates from native defects (possibly V-Ga) or complexes involving native defects has a reduction of peak intensity by about 70% when compared to undoped GaAs/Si. The crystal quality of GaAs on Si substrate with different In-content has been evaluated by etch-pit density.