The effect of an initial saturation coverage of antimony on the growth of indium arsenide quantum dots on gallium arsenide has been studied during metalorganic vapor-phase epitaxy. After depositing one to two bilayers of InAs at 723 K, the samples were quenched, transferred to ultrahigh vacuum, and characterized by scanning tunneling microscopy and x-ray photoelectron spectroscopy. It has been found that the critical thickness for onset of quantum dot formation is 33% less with Sb present as compared to without Sb. The antimony incorporates into the quantum dots, increasing their density and total volume, and causing them to be more densely clustered together.